Optimizing Programs, how many is too many and do they realy work?

Hello Experts,

First, I would like to start by saying I am a computer novice. 18 months ago I couldn't tell you how to turn on a computer. However, in that time, I've spent more hours than you could imagine teaching myself mostly through trial and error. It seems like there are conflicting answers to my question. I have several optimizing programs installed on both of my computers. The first one found over 1000 errors. Needless to say I purchased it and started running it once a week. Right after running it several months ago I ran across another one that offered a free scan of my computer. My god, it found 500+ errors that apparently the first one missed so of course I purchased it and started running both once a week. I came across one that didn't do the same thing the others did plus it gave me a score to go by. Naturally I had to get that one also. While researching a nagging problem I'm having with one, I came across this web site and went for the free trial offer. In one of the forums it mentioned a cleaning program and tried the free scan. Holy smokes, 427+ errors. I guess by now you already know my question. A computer Savoy friend of mine said they don't do any more than disc clean up and defrag do and they could actually do more harm than good. I asked this same question to 3 different computer techs and got 3 different answers. With all the experts here, I'm hoping I can get a straight answer. Do they really work? Is running more than one a bad thing? The ones I have are suppose to be the top rated programs. Now I wonder if they really are. The three I have on this computer are; RegCure, UniBlue Power Suite, and PC PitStop. Thank you for your time. I hope I haven't wasted it.

Rick Burton