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.