[b]-Cleaning the Prefetch Folder-[/b] [i]Myth - "Deleting the contents of the Prefetch folder improves performance."[/i] [b]Reality[/b] - Deleting the contents of the Prefetch folder will reduce application launch and windows boot time performance. Every time you delete an application's Prefetch (.PF) file you will cripple that application's load time the next time you go to launch it. Even though Windows XP will simply re-create that application's Prefetch (.PF) trace file, that application's optimal load time will not be restored until after the second time you launch that application and the system has been able to go idle and fully run the prefetch optimization. Windows XP automatically cleans the Prefetch folder down to the 32 most used Prefetch (.PF) trace files when the folder reaches 128 files so they do not needlessly consume space. This cleaning is only done when the system has gone idle. Prefetch (.PF) trace files are not a cache and are not preloaded into memory upon windows startup. They are never even accessed until you launch an application. Only one Prefetch (.PF) trace file per application is created. There is never ANY reason to delete these files. [b]Laptop Users[/b] - Windows XP will not execute idle tasks when running on battery power and thus cannot fully optimize prefetch performance and clean the folder (if necessary). You can manually force this to run by going to "Start", "Run", Type [b]Rundll32.exe advapi32.dll,ProcessIdleTasks[/b]. This can take 10-15 minutes to run but no notification will be given when it is finished. You will notice increased Harddrive activity while it is running wait until this stops. If you frequently run only on battery power it is recommend to do this once a month. [b]Malware/Viruses[/b] - Some people irresponsibly recommend cleaning this folder due to possible Malware/Virus infection. Malware/Viruses can place an infected file(s) in any folder and the Prefetch folder is no different. Do these same people recommend deleting the contents of the Windows folder because it is a popular location to find an infected file(s)? Of course not, you simply clean or delete the infected file(s) not the contents of the folder. This Myth got started due to the indiscriminate nature of the Windows Prefetcher, which will Prefetch any executable file that you load or loads during Windows start up. Thus it is quite common on an infected machine to find a Prefetch (.PF) trace file in the Prefetch folder with the same name as an infected executable. These files are NOT Malware/Viruses. They are there to improve the load time, in this case ironically, of the Malware/Virus but do not contain any infected code. Once the associated infected executable is deleted, these Prefetch (.PF) trace files do nothing and will eventually automatically be cleaned by Windows. [b]Corrupted Files[/b] - Some people claim that Prefetch (.PF) trace files can get randomly "corrupted" and thus they need to be periodically deleted. Files do not get "corrupted" unless something is wrong with your computer. Any file corruption is a warning sign something is wrong with your system. Overclocking, using defective components like Memory and Harddrives and using FAT32 instead of the superior NTFS file system are common causes of file corruption. NTFS is very resilient to file corruption as compared to FAT32. When storing data to disk, NTFS records file I/O events to a special transaction log. If the system crashes or encounters an interruption, NTFS can use this log to restore the volume and prevent corruption from an abnormal program termination or system shutdown. NTFS doesn't commit an action to disk until it verifies the successful completion of the action. This precaution helps prevent corruption of an NTFS volume. NTFS also supports hot-fixing disk sectors, where the OS automatically blocks out bad disk sectors and relocates data from these sectors. This housecleaning happens in the background. An application attempting to read or write data on a hot-fixed area will never know the disk had a problem. Thus the solution is fixing the cause of the file corruption. [b]CCleaner[/b] - Finally the useless, performance slowing cleaning option "Old Prefetch data" was moved to the advanced section and is now not selected by default. Never select this option for cleaning as it will increase application and Windows load times. This option removes Prefetch files that are a few weeks old based on the NTFS last access date. Since Windows XP already cleans this folder at 128 entries, this is a useless option that will only reduce system performance. You should never delete a Prefetch file for any installed application since that would cripple it's load times. Just because a program was not used in a few weeks does not mean you want it to load as slow as possible when you do decide to use it. If you disable the NTFS last access date stamp then this option will delete the whole contents of the Prefetch folder after a few weeks, which will cripple Windows Boot and all application load times. The Prefetch folder is also ridiculously small so cleaning Prefetch files before the 128 limit will reclaim next to no disk space. This option clearly needs a warning to prevent people from unknowingly hurting their system performance. Anyone who claims this should be cleaned for ANY reason does not understand how Windows Prefetching works. [b][i]Bad Advice[/b] - This bad advice to clean the prefetch folder is posted frequently on the Internet by people who do not understand how the Windows XP Prefetcher works. Their explanations are 100% inaccurate.[/i] NEED SOME REPU:crybaby:

Last edited by Zander (2008-10-23 03:06:02)