A couple of users on my network have recently reported issues with Windows generating new user profiles for them at log on. As expected they are not happy "losing" their data & settings. Luckily Microsoft has a tool to fix this problem and it is very easy to use. It is called the User Profile Hive Cleanup Service (UPHClean).
Microsoft Knowledge base article 837115 gives you the description of the errors it fixes and a link to the download.
