I'm going to assume that you have a corrupted windows user account? If so, give this a read http://windows.microsoft.com/en-ca/windows/fix-corrupted-user-profile#1TC=windows-7. I have had this problem in the past and was able to get it fixed up no problem. Basically you are going to create a new account, log into it, find the files from your old account and copy them over. That link is for Windows 7, but should be similar for other versions.