I had the same problem. I have a workaround if System Restore fails to
correct this. For me, It even occured in Safe Mode.
1. Make your way to starting Internet Explorer
2. on the address bar type:"control panel"
3. go to User Accounts...-> Add User account-> Create New "Admininstrator"
Account.
4. Shut down manually if you have to and reboot and access the new Admin
account
You will now have new account with all original programs still installed and
access to old files via either:
a. Internet exporer-> Address bar-> type: C:\users\ your old user account name
b Start button-> computer-> C:\Users\ you old user account name.
* You'll find here folders which will contain you old docs, downloads, etc
from you old account.
Thanks,
spawnocula