there is no reason to remove prefetch files... it's a myth perpetuated by those who don't understand it; If it was faster to NOT use prefetch files, would MS simply not have implemented it?
The other argument is that when you have too many prefetch files it can slow down application startup. This is also untrue, since the files are indexed by executable name- Windows doesn't look through every single file to load up the proper prefetch, it recreates the same prefetch filename and tries to open it. Either it exists or it doesn't; If it does, it opens it and examines the prefetch data (generally telling Windows which parts of the executable to load up first, since they get accessed more.) If it doesn't exist, windows creates it, and then profiles the application startup. *THIS* is much slower then even the mythical gain in performance from deleting the prefetch files.
