I regularly carry out disc maintenance (usually once a week) running Disk Cleanup, Chkdsk, Disk Defragmenter, and searching for and deleting *.tmp files.

Recently, on searching for *.tmp files, I found a large number of files of the format ~DF*.tmp in the directories:-
C:\Documents and Settings\[username]\Local Settings\Temp

These have only appeared during the last few days. For each user, there are two of these files for each logon time and each are 32KB in size.

Does anyone know what creates these files and why they are not automatically deleted on logout?

I am running Windows XP Home Edition SP1, and the only changes I have recently made to my system are:
3rd May - Installed Microsoft AntiSpyware (Beta)
10th May - Installed Windows Malicious Software Removal Tool - May 2005 (KB890830)
11th May - Installed Microsoft Windows Rights Management Service Client with Service Pack 1
15th May - Updated Adobe Reader 7.0 to Version 7.0.1