Should I just chunk this computer?

I'm stressin here b/c I don't know all this comp lingo and don't know how to find out what's wrong with my computer. The comp tech says I have 7 viruses, no backup disks have ever been made and that I have to pay him 175 to "maybe" fix it. What to do? I don't know where the problem lies in the computer, should I just buy a new one? I NEED HELP!!! I'm taking 3 internet cles in college and can't not have a computer. lol So....trash it or pay the big bucks. Is it fixable?