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The problem is that most users only have around 40-70 programs and services that they run on a regular basis. Which means the prefetch data will remain for an additional 58 to 88 programs before they get deleted. This will mainly include system updates and demo software, that are only run once or have been removed. You'll also have a record of all the exe filenames you've run (including any bits of dubious software!)
The prefetcher automatically cleans uninstalled applications and remaining files take up next to no space..
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CCleaner will remove the prefetch pf files that haven't been accessed in the last 2 weeks, so removing the old and unused ones, but leaving all the programs you use most as fully optimized. Granted this will only save you a small amount of diskspace, and isn't protecting your privacy to the extent of IE History cleaning, but then the prefetch cleaning is only a minor part of CCleaner.
It shouldn't do this at all. It shouldn't remove any application that is still installed on your machine. It removed applications I use everyday. It is removing files based on the file date. It should only be removing applications that are no longer installed on your system which the prefetcher does automatically. The space saving argument is useless since you want a PF file for ANY application you have installed incase you run it again.
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I know fully well you could say, "what about the fact it will delete the prefetch data for the program I only run once a month?"... or "what if I go on holiday for two weeks and then come back?"... or "I've turned off the LastAccessedDate property on my file system so it deletes all the pf files." ... or "I'm in love with my .pf files and don't want anyone to touch them!"
If you think these factors affect you or are highly important then I'd thoroughly recommend you turn prefetch cleaning off, if not then leave it the box checked.
It shouldn't even exist at all there is no reason to delete these files.
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Either way in the vast majority of cases running the prefetch cleaning option in CCleaner will optimize the system (reduce the number of unnecessary files) and not degrade performance.
No it UNoptimizes the system by deleting .PF files for applications you use everyday. Anyone can test this themselves. And this should have been tested to begin with.