So, I logged on as a local administrator and checked the size of the profile and disk space on which the profile located. The profile size seemed normal and there was enough space on the hard drive. I deleted the user's profile in Control Panel and asked him log back in: no error message popped up. However, a few days later, the problem happened again on the same computer under his account.
There are many different reasons for this error. The only way to figure out the cause is to turn on user-environment debug logging. For more information about how to turn on this log, see http://support.microsoft.com/default.aspx?scid=kb;en-us;221833.
This was first published in December 2003