Problem Deleting Prefetch data with CC Cleaner 2.30.113 in CCleaner Suggestions Posted May 14, 2010 Augeas, I think that the internal defrag operation which takes place every three days (Windows XP) uses the MRU (Most Recent Used) lists in the registry and perhaps information from the ""recent"" folder as well to re-build or to add information to ""Layout.ini"". In the registry Windows XP keeps track which folders and/or files the user has opened. See e.g. my last post in this thread http://forum.piriform.com/index.php?showtopic=27868 So, wiping the 1) prefetch folder, 2) MRU lists in the registry, 3) ""Recent opened"" folder regurlarly does prevent ""Layout.ini"" from filling with obsolete info and that speeds up the internal defrag process. Because then it contains less information that needs to be processed.