Does prefetch folder clean itself from non existent entries?

Some people say that periodically deleting everything in \Windows\prefetch folder can speed up system boot and perfomance. From my personal experience deleting that folder’s content actually slows down system boot for a few restarts (untill it rebuilds itself). The folder contains info to load certain programs faster in ram… or pre-load them. Certain programs being whatever is in autorun and most frequently used programs. I think some people belive that deleting prefetch folder speeds system up because if you let’s say, remove lots of stuff from autorun, data on those items will still remain in prefetch, thus slowing boot up. So my question is: does prefetch cleans itself from non-existent items \ entries? Or maybe it’s limited to a certain number of enties, and whenever it is reached, simply oldest ones are deleted? Or, parhaps, it doesn’t really impact system perfomance, even if there are junk (obsolete) data there?

P.S. I personally think it doesn’t worth messing with it, but I wanted to know if it can (efficiantly) take care of itself.

I am not aware that Windows does any housekeeping there, you can use CCleaner which has an option to remove ‘old prefect’ items, but I’m not sure how good/bad that helps.
I think with current hardware this ‘tweaks’ should be hardly noticeable.

Good idea. However, if you’re running an SSD, you might think about changing it’s behaviour. The settings can be found at - HKEY_LOCAL_MACHINE\SYSTEM\CurrentControlSet\Control\Session Manager\Memory Management\PrefetchParameters:

0 = Disabled
1 = Application Launch Prefetch
2 = Boot Prefetch
3 = Prefetch All
Exit Registry and Reboot

but I wanted to know if it can (efficiantly) take care of itself.

The short answer is yes, it does look after itself, but it’s a pretty complicated process - If you’re interested, read chapter 9 of the book Windows Internals.