When I try to use the "Turn Windows features on or off" function to add or remove anything I get "An error has occurred. Not all of the features were successfully changed." I need to remove Microsoft .net framework 3.5.1 plz help me 

My Computer
At a glance
Windows 7 Ultimate x644 Gig
- OS
- Windows 7 Ultimate x64
- Memory
- 4 Gig