Unless you're running Windows 9x you should never use apps like that. The memory management of XP is completely different and much more efficient, and apps that "free up" RAM actually do more harm than good. XP allocates as much of the available RAM as possible so that it can provide a large chunk of it instantly when the need arises. What you see as used RAM is really "RAM that windows holds on to so that it can be made available quickly". IOW, freeing up used memory this way makes everything slower as the OS needs to grab it again and then hand it out to the programs that need it. There should never be any significant amount of "free" RAM. More in depth info .