It's nothing like that, I think it runs in the background, don't even know if there is any option to control it. I think bootvis does exactly that though, that you can run the optimization whenever you want, not just when it's scheduled. But power over what to place? No, just automatically after how they are used and accessed, which is the better way anyhow. Probably why Task Scheduler is needed for Prefetch to work as intended, and the defragment-program. Mastertech: Hehe, read my test again, after I tested with prefetch off and cleared the cache (I can only clear something that is there from the beginning, right ) I restored it from the backup I took, I have the files there, 129 if I can remember it correctly, maybe some hidden also. Prefetch works for me, not just the defragment part. I actually used the option in nLite to preserve Prefetch functionality.