I have been trying to delete some files that are in my temp Int. file and they won't delete. It keeps saying I am either using the files with another program or someone else is. Since I am the only one on here the second is impossible. The first part is nuts because I am not using other software at this time and my programs in my task bar are all idle at the moment. Since I think I have some not nice files, this sounds pretty suspicious, one of them is Pefdata - f4 and others that start the same. Any idea why I can't get rid of these rascals. a

   Evidently Windows or another program is using them.
   You may need to boot the computer using a different operating system (use a boot CD for DOS, Windows, or Linux) and delete them from there.
   Our XP Recovery CD Maker will work for this if you have a Windows XP computer to make the CD with.

I would urge CAUTION in deleting files, especially those which are specified as being in use.  You might download the "Unlocker" program and use that to see exactly what software is using the files you want to delete.  

The perflib files are used (on my XP computer) for display drivers related to ATI software.
Laverne

Be careful with Unlocker. I downloaded it from different sites and allways found adware with Emsisoft Anti Malware. Finaly I found one that was clean.

You can delete these files by entering safe mode on startup, keep pressing F8 until the menu appears.
But personally I would be wary. Perfib.dat is a windows file that you need though why this is in your temporary internet files folder is another matter. Perfib.f4 would seem to be possibly a version taken over by another program either legitimate or not.

I would normally check by changing its name (in safe mode) to, for instance perfib.txt and restarting normally to make sure everything is working as it should. If it is, belt and braces, copy the file to a stick and delete it from the hard drive.

Rename the file on the stick to the original and run a virus check on it.

You may need to run System File Checker after all of this to make sure whatever changed this file didn't change any more files.