I've always rather enjoyed people saying "I've always used it, it makes my PC faster" or something to that effect (where it is pretty much anything- a registry cleaner, a "tune up" program, etc).
If they have always used it, how do they know it makes their computer faster? They don't, and in all likelihood it doesn't.
Take one of the most invasive "Tune up" type program I've had to deal with. "System mechanic". It's supposed to make your computer faster. That's what they all claim. But somehow I don't see how adding 3 new background processes that consume about half my RAM when added together and decide to "defragment the registry" at seemingly random intervals (well not random, it appears to purposely choose the most inopportune time "Oh hey, I know I've just sat here for the last three hours as you weren't using the computer, but I decided to wait until you tried to play quake to monopolize the CPU".
I swear they do it on purpose. because the types of people who buy these programs never suspect the program. Oh no- it must be a virus or something equally malevolent. And some of them may call tech support, where they can be encouraged that the latest version of the program makes your PC run even faster!
Of course, the funny thing is, they are usually wrong. each new version adds another layer of useless features. Have you seen these programs lately? Every single one of them has decided that they deserve their own unique skin. Why? It's a tune up program, not a bloody beauty pageant- at least, it shouldn't be. Actually, it is.
I would bet money that if I — or anyone, for that matter — was to create a "optimizer" program that did <absolutely nothing> but looked absolutely stunning while doing it (of course, it gives the <impression> of doing things, listing filenames, progress bars, so forth) people would swear on the great possum that it actually works faster then any of the other "tune up" programs on the market.
Generally speaking, any type of program where the majority of commercial offerings have a non-system default skin is a type of program you don't need.
