For Windows Vista and 7. This might have happen to most of us. When you log in your profile, you get a popup on the bottom right that says ‘You have been logged on with a temporary profile. You cannot access your files and files created in this profile will be deleted when you log off. This sometimes happens when the username has either been changed or the folder of the profile has been deleted. So Windows will continue to look for it and leave you with a temporary profile. To fix this you need to make the following to restore the folder.

:: Log on the machine as an Administrator
:: Click on Start and type regedit
:: Find the following key: HKEY_LOCAL_MACHINE\SOFTWARE\Microsoft\Windows NT\CurrentVersion\ProfileList
:: There are a lot of folders in the key. Find the ones with the .BAK at the end
:: Delete the profiles in question with the .BAK extention (Make sure you take a backup of the registry first)
:: Close Regedit
:: Restart PC

After you log into the computer, the profile folder you are having problems with is re-created.