FYI about my own experiences with System Mechanic. Like BGCBGC, I had tried SM several years ago. At first l liked it, but there came a time when it, as I recall, deleted a stuff that, in hind site, shouldn't have been deleted, thereby causing me some WindowsXP grief. Sometimes it isn't always easy to know what it is that's being deleted, and when a program is a little too aggressive in that regard, that can cause problems, as it did for me. Unless your a computer whiz kid who absolutely knows what's being deleted, I think it's better to error on the side of caution by using programs that may be kinder and gentler, and a little less aggressive than SM, about deleting files that you may or may not need deleted. I then tried an IO Bit program for awhile, (altho I can't recall the name of it right now..), that was also supposed to keep my system clean. But it installed itself memory resident at boot up and it slowed my whole computer down. So I abandoned it, plus it seemed like it constantly nagged me about all other IO Bit programs, as well. Hence, this is why I'm happier after discovering and using CCleaner. (The free version). It asks - only occasionally - if I want to update to their professional version, (which I just might do one of these days), otherwise, it just tells me when there's a new version available for download and install. It has kept my system humming right along. I don't recall anything NOT working right after I've run CCleaner and I use it daily, and religiously, each and every time I shutdown my computer. That whole process takes, maybe, 20-30 seconds depending upon how much I've been surfing the NET and how fast my fingers and my mouse moves.