GWT....dont ditch the computer....Just wipe the disk clean and reinstall windows and any other software you added.
You probably downloaded a trojan horse program on your computer from a website. It could have started as something innocent as a smiley face program to put smileys in your documents.
Little did you know that the free software would turn your computer into a monster and fill the screen full of pop-ups and shit.
After you clean the hard drive, install a good pop up blocker or a free cleaning program like ad- aware, a virus scanning program...you should be all back to normal.
I had the same thing on mine, ad aware could not even clean it up. It stole my bandwith on my dsl line and made everything legitimate load slow....since it took over my machine and downloaded the trash. Ad aware can keep things clean once you restart, You can get the program from the following website:
http://www.lavasoft.de/
If you have not used this program, download it and try it first before you erase everything.