First up, I admit the atrocities of dll hell. But this post is not about it :o) If you have ever thought of OR needed an online database that contains information about DLL/EXE files that are included with selected Microsoft products, you may like the following information.
This one comes in quite handy at times... http://support.microsoft.com/dllhelp/
So, if you want to know about the default version of aspnet_filter.dll which comes with .NET Framework 2.0, Type aspnet_filter.dll in the File name text box below... and click on Search to find more information for the dll!
If you click on More Info hyperlink you will find another good list of handy information which is pretty difficult to get without using any specific tool!