Hi,
"You may have several versions of the .NET Framework installed on your computer. Each version of the .NET Framework can co-exist with the other versions on the computer."
Cf.:
http://msdn.microsoft.com/en-us/kb/kb00829019.aspx ("Benefits of the Microsoft .NET Framework").
You need al the versions of the .NET Framework.
Hope this helps,
Vincenzo Di Russo - Microsoft MVP Windows Internet Explorer, Windows Desktop Experience & Security - Since 2003. ~~~ My MVP Profile:
https://mvp.support.microsoft.com/profile/Vincenzo