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Everytime I boot to XP, I get files with names such as "Perflib_Perfdata_294.dat" in my temp folder, and I can't delete them. They change every time I reboot, but I have not been able to find out which app. is writing them, or whether they are harmful. I have run a full scan with both AVG and Kasperkey, both of which ignore the files. Any info?

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You might want to edit your question and think of a better subject. – innaM Aug 19 '09 at 11:32

These are created by any program that installs a performance-monitoring function. They get created when the program runs, which would explain why they change every time you reboot. You cannot delete the file that covers the current session, but you should be able to delete any old files that are still about. However, these should get deleted on reboot.

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These are system performance monitoring files from Windows.
Look at this discussion.
It refers to this Windows tool,
Windows 2000 Resource Kit Tool : Extensible Performance Counter List (exctrlst.exe)

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These files are related to the Windows Performance Counters. No idea what they are actually good for, but here is a longish post that explains how to disable them:

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It is used by Performance Monitoring. These files are the temporary log files generated while the basic performance monitors tasks are running.

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Sometimes, if you try and delete them right after you boot up, you can delete these files because the program using them has not started yet. Otherwise, if you really want to delete the files, scramble the data with a file shredder and use an admin account to delete the files.

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