Windows 7 switch user hangs

[Guest]

Hello,
When switching user the OS hangs after 20 30 seconds from password being entered to blank screen. Any ideas for trouble shooting this problem.
Win7x64.
Nick

 

[number13]

open an command prompt (All Programs, Accessories, right click on Command Prompt and select Run as Administrator" ), in the cmd prompt type sfc /scannow see what happens and let us know how it goes