Computer help

[Witty]

I'm sure this has been asked before, but I've been searching the web for almost a week now, so I'm tired of searching.

I bought the computer (HP dc5000 SFF) a few years ago from the school. They were selling them to make room for the new computers. I bought it for $50 (kinda cheap) which came with everything (mouse, keyboard, etc.)

For the past few weeks, my computer has been really slow. I've defraged it several times and done some virus scans, thinking that would speed it up. It never really did anything. So I got to thinking. it might need a good factory reset, but here's the problem. It never came with a CD.

So I was wondering, can you factory reset a computer without a disc?

If you need anymore information about the computer, feel free to ask.