Came across this error today when the user logged into their PC:

windows\system32\config\systemprofile\desktop is not accessible

All kinds of problems and random errors then started appearing.   I also found various services weren’t starting such as Network List and User Profile Service.  The errors in the event log when starting the services were “module not found”.

First thoughts were maybe a virus, but after scanning with several tools, I came to the conclusion that it’s looking like some kind of disk corruption on various OS files.  Had to first run chkdsk /r (then reboot to run at startup).   This found errors and corrected them, but the problems still appeared.   Finally had to run sfc /scannow which took a while to run, but got there eventually.  Problems solved!

Note the sfc command reported errors with the sidebar which it couldn’t fix.   This appears to be a vista bug according to the following knowledge-base article: