Mailbag: Do I need still need older versions of the .NET Framework on my system after installing .NET Framework 3.5 SP1?


I recently installed the .NET Framework 3.5 SP1 on my system.  Afterwards, I looked in Add/Remove Programs, and it shows that I have all of the following versions of the .NET Framework installed on my system:

  • Microsoft .NET Framework 1.0
  • Microsoft .NET Framework 1.1
  • Microsoft .NET Framework 2.0 SP2
  • Microsoft .NET Framework 3.0 SP2
  • Microsoft .NET Framework 3.5 SP1

Do I need any of these older versions of the .NET Framework now that I’ve installed the .NET Framework 3.5 SP1, or can I safely uninstall them?


When you install the .NET Framework 3.5 SP1, it will also install the .NET Framework 2.0 SP2 and the .NET Framework 3.0 SP2 behind the scenes.  You cannot use the .NET Framework 3.5 SP1 unless you also have the .NET Framework 2.0 SP2 and 3.0 SP2 installed.  Therefore, you will not be allowed to uninstall the .NET Framework 2.0 SP2 or 3.0 SP2 if you have the .NET Framework 3.5 SP1 installed.  If you try to uninstall those versions of the .NET Framework, their uninstall processes will block and tell you that they are needed by another application on your system.

The .NET Framework 1.0 and .NET Framework 1.1 can be installed side-by-side with the .NET Framework 2.0, 3.0 and 3.5.  Most applications that were created for the .NET Framework 1.0 or 1.1 will automatically use the .NET Framework 2.0 instead if it is installed on the system.  In most cases, that means you do not need to keep the .NET Framework 1.0 or 1.1 installed on your system if you already have the .NET Framework 2.0 installed.

However, there are some applications that are configured to require a specific version of the .NET Framework, even if later versions of the .NET Framework are installed.  If you have any applications like that on your system and try to run them without installing the .NET Framework 1.0 or 1.1, you will get an error message that looks like the following:

MyApplication.exe - .NET Framework Initialization Error
To run this application, you first must install one of the following versions of the .NET Framework:
Contact your application publisher for instructions about obtaining the appropriate version of the .NET Framework.

In the above error message, the version number will be v1.0.3705 if you need to install the .NET Framework 1.0, and it will be v1.1.4322 if you need to install the .NET Framework 1.1.

If you end up seeing any error messages like this, you can re-install the .NET Framework 1.0 or 1.1 in order to resolve the errors.  If you don't end up seeing any error messages like this, then you don't need to worry about re-installing the .NET Framework 1.0 or 1.1.

Comments (44)
  1. Bob's Nieuws says:

    De afgelopen periode was nogal een periode van veranderingen. Zo was er de bijna overname van Sun door

  2. gl1200phil says:

    Many thanks Mr Stebner!  All the heartache and frustration of MS is assauged by all the kind folks like you who offer so much great help out of the kindness of your hearts!

    Peace and Blessings! from Belly-view

  3. sleuth says:

    Thank u for the answer, to the point and informative!

  4. Leo says:

    Do I need the .NET Framework 3.5 SP1 now that I’ve installed the .NET Framework 4?

    Or can I safely uninstall .NET Framework 3.5 SP1 after I've installed the .NET Framework 4?

    Thank you.

  5. Hi Leo – By default, the .NET Framework 4 does not allow all applications built for earlier verisons of the .NET Framework to migrate forward and run on it if the earlier versions are not installed.  If you are using any applications that were built with any version of the .NET Framework before version 4, then I would recommend leaving both the .NET Framework 3.5 SP1 and 4 installed.

  6. Leo says:

    Thanks for the info. That's what I suspect too.

  7. phespy says:

    Does the same apply to XNA framework versions?

  8. Hi Phespy – No, this guidance doesn't apply to the XNA Framework.  Each version of the XNA Framework is completely side-by-side and does not know about any other versions.  You must make sure that you deploy the exact version of the XNA Framework that your game is built against, even if any other versions of the XNA Framework are already installed on the computer.

  9. phespy says:

    Thank you very much for the help and quick response

  10. MaxBn says:

    Thank you for your response, it answered my question on Net Framework.

  11. Shawnee says:

    The .net framework is taking all my memory :/ … (yes, it's an older beater laptop with a C and D drive with 19 & 17 GB.  Anyone heard if they are coming out with a newer version or something that can replace all those memory hogs??? Love to delete 1, 1.1, 3.5, 4.0 etc. tired of that little icon at the botton saying almost out of memory space. Thanks for your comments

  12. Hi Shawnee – Each version of the .NET Framework is designed to install and run side-by-side with older versions, so there won't be a new version that replaces all of the previous ones.  That being said, most older .NET applications will run correctly if you have 3.5 installed and you can probably uninstall the .NET Framework 1.0 and 1.1 from your computer if you are low on disk space.

  13. Shawnee says:

    Ugh… hope they modify that someday… thanks for the advice… I'll give it a try. Merry Xmas 🙂 S.

  14. auee says:

    This is very informative THANKS for such clear and helpful answers!

    My only problem now is the Windows Security Update for 3.5 won't install on my Windows 7. I've already got .Net 4.

    Should I be worried? I've tried pretty much everything to sort it out but I'm not getting anywhere.

  15. Sherry Hodge says:

    Thank you so much,your knowledge is awesome and extremely helpful. I just wish microsoft,Thanks again 😉

  16. Brian says:

    Gee, would I like to kick Bill Gates in the pants. This miserable garbage system he is growing is costing us a fortune. If IBM had just taken up 'Oasis'(theos) when offered we would have super speed now without the $billions spent on massive equipment to overcome Gates.

  17. calin says:

    so what i don't understand is: if let's say i don't have any .net framework on my pc if i install version 4 or 3.5 they won't work because i don't have the previous versions?… i really doubt that.

  18. Hi Calin – The .NET Framework 4.5 and 4 don't require any other versions of the .NET Framework in order to run correctly.  The .NET Framework 3.5 is essentially just an add-on though, and it requires both the .NET Framework 2.0 and 3.0 in order to run correctly.  The installer for the .NET Framework 3.5 will install all 3 of those versions automatically though, so you don't need to worry about forgetting to install 2.0 or 3.0 in this scenario.

  19. George says:

    Thank you for your help. It was clear and saved me a lot of time.

  20. Paul says:

    Great Teachers!

    From humble student.

  21. JT Dodge says:

    Nice primer. Thank you.

  22. MJ says:

    I've said it before– I'll say it again.  YOU ARE THE BEST!!  Even if half the time I fail to fully understand your cogent, concise instructions.  I remember one time I even emailed you and you wrote back.  You are a true blessing for so many not so informed…

  23. MJ says:

    It finally worked.  Running VISTAx32.  Uninstalled the .NET Framework 1 and followed netframe repair tool and ended up following in order the numerous updates…  All in all, up to 22 of 'em. Through .Netframe 4 et seq.  Not sure I need them all, but OS's running great!!

  24. Hi MJ – I'm glad to hear that you were able to resolve the .NET Framework issues on your computer, but I'm sorry for the hassles that these issues caused for you in the first place.  Also, thank you for the kind words.

  25. neece says:

    so after reading all above are you saying that network 4.5 or 4 needs to be installed and the others dont have to be installed since 4.5 doesnt need them to perform correctly. because i have 1.1 ,2.0,3.0,4 client profile ,and 4 extended do i need all of that installed

  26. Hi Neece – You're correct.  The .NET Framework 4.5 doesn't require any other versions of the .NET Framework in order to work correctly.  Not all applications will work correctly if you only have the .NET Framework 4.5 installed though, so it still might be necessary to install some of the other versions of the .NET Framework on your computer depending on what applications you use.  I wrote an updated version of this blog post that includes information about the .NET Framework 4, and it might help for you to take a quick look at that post too.  You can find it at…/10219046.aspx.

    One other note too – the .NET Framework 4.5 is a full replacement for the .NET Framework 4, so it isn't possible to install both the .NET Framework 4.5 and 4 on the same computer.

  27. kinzo says:

    Thank you very much for the lessons……..just one more quickly, how do I uninstall NET 3.0 on my pc ???

  28. Hi Kinzo – The answer to that question depends on what version of Windows you have on your computer and what other versions of the .NET Framework you have on your computer.  If you have the .NET Framework 3.5 installed, it requires the .NET Framework 3.0, so you won't be allowed to uninstall 3.0 out from under 3.5.  Some versions of Windows come with the .NET Framework 3.0 (Windows Vista) or 3.5 (Windows 7, Windows 8, Windows 8.1).  In those versions of Windows, you can enable/disable the .NET Framework 3.0 and 3.5 by going to the Windows Features control panel (optionalfeatures.exe) and unchecking the .NET Framework 3.0 or 3.5 item listed in there.

  29. Kathy says:

    I have Windows XP Professional SP3 and I was looking at my list of programs one day quite awhile back and wondered what .NET Framework was, I googled it at that time and I read it was something used by developers.  I was able to remove some of the updates I had in my computer.  However, that seemed to start some problems and I then wondered why the computer let me delete the updates if they were needed.  I hired a technician and he removed them all and downloaded only .NET Framework 1.1 into my computer but that's it.  Don't I need more updates?  I wonder how their absence is affecting my computer as I have noticed it is slower, etc.  I have no knowledge of how .NET Framework affects computers and their efficient operation…Thank you

  30. Hi Kathy – You don't necessarily need a version of the .NET Framework until you try to use an application that requires it.  Installing or not installing it won't affect the speed of your computer.

    You can see more details about what the .NET Framework is by looking at this page on Wikipedia –…/.NET_Framework.

  31. Kathy says:

    Thank you Aaron.  I was lead to believe that because I didn't have all the updates I was not getting all the necessary Windows updates to my computer.  Thanks for the clarification

  32. Nick says:

    My dilemma is that I intend to go on using my W.XP computers for years to come, as I still use DOS, W.95, W.98SE, W.7…

    Should I install all the available updates, including all the .NETs to cover my back when MS delte the update service?

  33. Hi Nick – Yes, I'd recommend installing all available updates on your Windows XP computers and also to enable Windows Update so you can keep up to date in case any further updates are released in the future.

  34. Nick says:

    Thanks for the advice.  I've now installed the lot, except for the smart card and search add ons and media player 11.  Might still add the latter…  Then will clone my disk!

  35. says:

    Aaron, I was wondering about your note about some applications built in .NET 1.1 using .NET 2.0 if it is available instead. How is this decision made? I've got some portions of a large application developed in .NET 1.1, and now we are looking at pushing the app to a Windows Server 2012 box. I understand that .NET 1.1 is not supported on this box, so I need to find out if the app will automatically use .NET 2.0 instead.

    Is there any way to determine this without having to just try it? In my case, that is far easier said than done!


  36. Hi ChrisMikeC – There is a table in the MSDN topic at…/ms994381.aspx that explains what the behavior will be for a .NET Framework 1.1 application if the .NET Framework 1.1 and/or the .NET Framework 2.0 are installed on the computer.  To summarize that table for your scenario, if a .NET Framework 1.1 app is run on a computer that has the .NET Framework 2.0 installed but does not have the .NET Framework 1.1 installed, it will use the .NET Framework 2.0 at runtime unless the app includes a configuration file that specifically forbids it from doing that.

    If you need it, there are examples of configuration files for this type of scenario at…/jj152935(v=vs.110).aspx.

  37. Kathy says:

    Aaron, I was interested in Nick's comment about still using his computers with XP for years to come, as well as the DOS, Windows 95, etc.?  The fact he's been using computers with DOS and Windows 95 shows that it can be done without the Windows updates?  I love my computer with XP and it runs perfectly.  I hate buy a new laptop just because MS no longer supports XP.  I am in a dilemma about it.  I have MS Security Essentials and if I run a scan every night to catch threats, viruses, etc. will I be ok?  It's just that my computer won't look updated?  That's ok by me, I just don't want to have security issues

  38. Hi Kathy – I'd encourage you to read the post at…/end-support-help for more details about your scenario.  To summarize it, you will only continue to receive antimalware signature updates for Microsoft Security Essentials on Windows XP for a limited time, and Microsoft is no longer providing security updates for Windows XP.  As a result, you won't be able to keep your Windows XP computer completely secure now that support has ended for it.  I'd encourage you to start looking at updating to Windows 8.1 if possible.

  39. Kathy says:

    Thanks for reply, I really appreciate it.  Everything I read points to buy a new computer.  How then is Nick using his computers with old operating systems safely?  Is he not in the same scenario I am?  Or, does he mean he does not use the internet on those computers, just uses them for his files, etc.  This all confuses me.  My laptop was purchased at a high price and although I know they are much cheaper now I feel cheated.  It's like having a 10 year old car that you love and are told you have to junk it because someone might hack it up sometime.  Arrrg!  I have another anti-virus (Stop Sign) at my disposal for free, it was uninstalled by a Microsoft technician in order to install Microsoft Security Essentials.  I wonder if I can wait for Windows 9 and take my security chances?

  40. Hi Kathy – I am not sure what Nick's exact scenario is, but I'm guessing that either he isn't connecting his PC's to the Internet or he is just getting all of the currently available updates and then taking his chances.  Now that security updates are not being released for Windows XP, there is no way to be 100% secure on a Windows XP computer that connects to the Internet.

    I'm sorry for the frustration that this has caused.  You don't necessarily have to junk the entire laptop though.  Upgrade versions of Windows are relatively inexpensive, and Windows 8.1 will work on most PCs that are capable of running Windows XP.

  41. Jet says:

    im trying to install the .net 3.5 but once the setup is nearly finished the "use the turn windows feature on or off appear, but its already turned on, (already have the Microsoft .NET Framework4 Client profile installed) nedd help on this

  42. Hi Jet – Can you please use the tool described at…/6458047.aspx to collect all of your setup log files, upload the file named that this tool will create to a file server (such as, and then reply back here and provide a link that I can use to download your log files and take a closer look?

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