Microsoft recently released v2.0 of Microsoft Security Essentials (MSE) which is a great, free anti-virus solution for Windows. I recommend it all the time to my friends and family.
Unfortunately I ran into a little issue with it not installing correctly on one of my home machines running Windows 7. The first time I let it try to upgrade itself I ended up with an error 0x80070643. What I was then finding on subsequent attempts to install it was that when I commenced the install (by running the mseinstall.exe package) I would see mseinstall.exe in task manager but nothing would happen. Task manager showed that the mseinstall.exe process appeared not to be doing anything – it was “hung”.
After asking around some colleagues I learned that such a hang can happen sometimes in the case where MSE v1.0 has not fully uninstalled correctly.
If you think you might be hitting this issue there is now a KB article that details steps for manually uninstalling MSE v1.0 from your system:
How to manually uninstall Microsoft Security Essentials if you cannot uninstall it by using the Add or Remove Programs item
Even better news is that this article has a “FixIt” associated with it. The direct link to the US/English FixIt package can be found here (although you would be better to follow the FixIt link in the article so you get the correct FixIt version for your language/locale).
In my case I just ran the FixIt and then attempted the installation of MSE v2.0. This time it ran through without a problem!.