I have the same problem, I'm using XP Pro Version 2002 SP3, with .NET 4.0 (I tested the versions 3.0, 3.1 and 3.5)!
Does anyone have some idea?
From what I know, .NET Framework has nothing to do with the double folders. They are created from the multiple installs of SolidWorks. Personally, I would uninstall all of the versions from your PC, clean the registry of SolidWorks registry keys. If you search the forums there are plenty of examples on how to do this and reinstall fresh. This should restore all of the links to .NET and other MS redistribuitables.
This is a new installation running on XP Pro SP3
After accepting the Failed message another message appears
Program .... Program files\Solidworks corp\solidworks(2)\solidworks.exe
Abnormal program termination
I checked for updates to my OS and it is current.
Also, when I installed SW2011 it found but didn't delete or overwrite the older version SW2009 which was left over from when I was telle-commuting with a former employer, so it created secondary SW folders (solidworks(2), etc).
Does the NET Framework error have anything to do with the double folders or should I uninstall everything, SW2009 and SW2011 and star over?