If you see a balloon when you log on to a Vista machine that shows the following error message: then you have a problem as your user profile has either been deleted or has become corrupted. To resolve this issue, do the following:Rename the directory where the profile is stored.

Open regedit.exe, find HKEY_LOCAL_MACHINESOFTWAREMicrosoftWindows NTCurrentVersionProfileList, and delete the key showing your profile’s SID (you can use the ProfileImagePath value to help you determine which one it is).

Log off and then log on again.