TweakPrefetch is an easy to use application that is designed to manage you system's fetching. It allows the user to set separate parameters for Prefetch and Superfetch.
Note: emptying the Windows/Prefetch folder is not recommended and will cause a temporary performance drop in applications startup time. I added this function to allow advanced users to reset Prefetch data in case it might be necessary. Prefetching in Windows XP is better left at its default value for the 99% of the users.
However, someone prefers to set it to "Boot Only", in order to benefit from fetching only at boot time. For what concerns Windows Vista, default settings are still recommended for most users (especially for who doesn't use the PC for gaming).
Advanced users and gamers might want to disable Superfetch (to obtain an XP-like fetching, reduce hard disk trashing and prevent this function to interfere with games) or set it to "Boot Only" at least. Obviously, it's up to the users to experiment different settings and tweak fetching at their advantage.