It seems that I see PCs every day with the following warning in the event log:
Event: 1524 Source: userenv
“Windows cannot unload your classes registry file – it is still in use by other applications or services. The file will be unloaded when it is no longer in use.”
The error doesn’t seem to have any negative effects on the system, but my logs are just full of these warnings. It also doesn’t seem to matter which OS the machine’s running – Windows 2000, Windows XP, or Windows 2003.
The suggestions I found on eventid.net led me to the Microsoft User Profile Hive Cleanup Service (UPHClean).
UPHclean.exe is a tiny program that runs as a service. After I rebooted, it did it’s thing, and all my userenv errors went away!