On Windows 2000 the service deals with application event log event 1000 from source Userenv where the message indicates that the profile is not unloading and the error is "Access is denied". On Windows XP and Windows 2003 the equivalent events are 1517 and 1524 from source Userenv.
To accomplish this the service monitors for logged off users that still have hives loaded. When that happens the service determines which applications have handles opened to the hives and releases them. It logs the application name and what registry keys where left open. After this the system finishes unloading the profile.
Download: User Profile Hive Cleanup Service
View: Windows Support
To accomplish this the service monitors for logged off users that still have hives loaded. When that happens the service determines which applications have handles opened to the hives and releases them. It logs the application name and what registry keys where left open. After this the system finishes unloading the profile.
P.s. Downtime was apparently due to a network issue at our Hosts; appologies :)

i dont know why MS has not made this far more public, i only found out about this when neowin anounced it back in Feburary.
Really off topic but:
Is it fixed in SP2?
Where could I get a list of fixes for sp2? Googling provides no results (or else I am searching for something else..)
"Supported Operating Systems: Windows 2000, Windows 2000 Service Pack 2, Windows 2000 Service Pack 3, Windows 2000 Service Pack 4, Windows NT, Windows Server 2003, Windows XP"
The following handles in user profile hive *edited* have been closed because they were preventing the profile from unloading successfully:
lsass.exe (440)
HKCU (0x3a0)
"Windows saved user XXXXXXXXXXXX registry while an application or service was still using the registry during log off. The memory used by the user's registry has not been freed. The registry will be unloaded when it is no longer in use."
In use by WHICH "application or service"?!
Seems at least Windows Server 2003 now has detailed boot and shutdown logging so this kind of this could be traced. I hope SP2 will have it for XP.
Commenting has either been disabled on this article or you are not logged in. Click here to login or register, its free!
Note: Anonymous commenting is disabled in order to keep the quality of responses to a high standard.