Alright, I am new to this computer thing, and when I turn on my computer it reads ..."CPU is unworkable or has been changed, re-check soft menu" I have no clue what this means and how to fix it...If anyone can help, that'd be great.

That is not a good message to get. The CPU is the central processing unit, or the brain of the computer. To me this message means that your CPU is either broken, or windows is confused. I'm assuming that you didn't just change the CPU. I think the soft menu means the BIOS that you reach if you push delete when you start up. That's a rather complicated setup area that you REALLY don't wan't to mess with if you don't know what you are doing. The point is that for someone who doesn't know what a CPU is there is no easy or cheap solution to your problem. Seek proffesional help.

you also get this message if you run XP and have changed the CPU
you will need to do an XP repair

Ive had this problem before, but only on newly built systems and only on the first boot. What I had to do was enter the BIOS and change the CPU settings eg, Th clock multiplier and FSB etc. But if you dont know what a CPU is, dont even think about messing with the BIOS, get someone else to do it.
You could try this:
Take your computer to P.C World, buy a cheap component like a network card and get the boys at Pc world to fit it (costs £30), then they will fit the card - probably without checking the computer is working properly - and then you can the blame the CPU becoming unworkable on them!!! A bit naughty I know, but hay, it will save you loadsa £sssssssssss.