If not, is there any way to defrag computers on your domain through the server?

I have a computer that is running a little slower than it should. I tried to defrag and delete files that I no longer use, but I think there is spyware on my pc. There are sexual pop-ups on my pc and stuff about icons and smiley faces!! I do want to say that we have downloaded limewire on my pc and we use internet explorer to access the web. Pls help.