Replying to All right... what do you do when your computer explodes???

So my computer was compeltely messed up a few weeks ago, mainly because of my abusive music downloading. I gave up on trying to fix it so I had the drive changed and it was fine again. I had promised myself to keep it clean and not download anything.

But.. yesterday, I had an urge to download this one program, Guitarpro, I kind of needed it, and I don't need to explain why, really. So I downloaded limewire and told myself, since it was only ONE download, that nothing could happen. Wrong. After I got the file, I unzipped it and immediately my antivirus started going crazy, telling me "VIRUS FOUND!!!" Every five seconds or so. So I deleted the file I had just downloaded. Nothing happened. These shortcuts for ads started appearing everywhere on my desktop, and as soon as I opened explorer, pop-ups would go crazy. My comp would also offer me to install these weird programs every few minutes. I did add or remove programs and deleted stuff that had appeared out of nowhere, and I tried looking through every file, and now my antivirus didn't find any infected files. Pop-up blockers don't work... WHAT THE FUCK AM I SUPPOSED TO DO. I can hardly use my computer anymore after ONE DOWNLOAD.

I even tried formating it, but I don't know how. So can anyone either please tell me what to do OR explain how to format a PC (if it's easy). I'm begging you... this post is rather short, but I've been writing it for about 20 minutes due to the incessant pop-ups. PLEASE.