Summary: Windows uses several techniques to try to run as fast as it can for you. The prefetch folder is an aspect of one such technique.
I found a SVCHOST.EXE-2d5fbd18.pf located in C:\windows\Prefetch. Should I delete it? I regularly run an up to date anti virus scan and it hasn't noted this as a virus.
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Ignore the prefetch folder.
Seriously, there's nothing you need to do with it, and unlike some tips sites might suggest, there's nothing you should do with it.
You can delete files in it if you like, but it'll just slow down your system a little, and they'll probably reappear quickly anyway.
Now, as to why? It's Windows, trying to be fast.
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Without getting into a lot of hairy technical detail, the process that Windows goes through when you run a program is actually quite complex. There's just a lot of "stuff" it needs to do in order to load and run whatever software should be running on your machine.
The prefetch folder is simply Windows saving some of that work so it can be re-used later, when you run the same program again. Nothing more.
Now, svchost, as has been discussed on this site repeatedly, is a required Windows component that's run quite frequently. In fact, you likely have several copies of it running on your Windows XP or Vista machine right now. The first time Windows runs svchost.exe it saves some of the work, some of the calculations it makes, so that the second (and third, and fourth, and so on) time it runs it, it can simply skip those calculations and load up the work that it did before.
Updating the program invalidates those calculations, and that's why the filename has that string of garbage in between the filename and the ".pf". If the program changes for some reason, that's no longer valid and a new one will be calculated the first time the updated program is run.
Like I said, you can, and should, ignore the prefetch folder.
The reason I emphasize that is that there are apparently other sites claiming that if you periodically empty the prefetch folder you'll speed up your system.
They are wrong.
As we've seen, by deleting the contents of the prefetch folder, you'll force Windows to do more work the next time it starts running programs, as it has no pre-calculated information for a head start.
And Windows keeps only at most 128 items in prefetch, so it always contains information for the most recent and commonly run programs.
You can read more geeky goodness about prefetch from a Microsoft engineer here: Misinformation and the The Prefetch Flag, which includes this quote:
... not only is deleting the directory totally unnecessary, but you're also putting a temporary dent in your PC's performance.
I rest my case.
Related:
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What is svchost, and why is there more than one copy running? Svchost is a component of Windows. It can be confusing because more than one copy is running, and it often shows up in errors caused by viruses.
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Where is it alright for svchost.exe to be? Svchost.exe is frequently spoofed by viruses attempting to hide. The official copy should be in your Windows\system32 folder, but there may be others.
Article C3543 - October 24, 2008
might faulty data in the prefetch folder be a possible cause when programs keep crashing when you are starting them?
30-Oct-2008
I suddenly was having trouble using wordperfect 11 in that the first time I opened a file, it took 10-20 seconds to open. After that it worked fine, but if I closed wordperfect, the same thing happened everytime. It appeared wordperfect was going "someplace" and looking for "something." I cleaned out the prefetch folder and the problem resolved.
Posted by: Michael Kelley at May 26, 2009 8:31 PMOne of my students installed software and uninstalled and reinstalled (software not working because older version was installed after newer version, etc.)
Anyway, I'll be going to the dealership, today, so your answer probably won't get to me, but what about deleting JUST the files in the Prefetch folder that apply to this software?
Thanks and glad I found this site.
Jan
03-Sep-2009