What is the best and free software for removing every possible virus in windows xp?

I have so many virus that my comp is gotten so slow, my enternet speed has decreased and many other bad stuff for my comp. I really need help please. IF THE SOFTWARE YOU RECOMMEND WORKS, THEN YOUR POINTS WILL INCREASE BY 10 POINTS.

What is the best and free software for removing every possible virus in windows xp?
I hate to tell you this, but free software just won't cut it. I laugh at anyone stupid enough to trust their whole computer to "AVG Free"... it's absolutely pathetic. Trust me - I work as a network engineer - if you want virus protection, just trump up the small amount of cash (~ $40?) for something more adequate - McAfee Small Business / Enterprise edition is simply excellent, and adds so much more protection compared to the slightly cheaper Home edition. Don't go near Norton - all the professionals whom I work with agree it's disgraceful.
Reply:AVG free edition
Reply:The best free anti-virus out there is AVG Free Edition. The best free software for removing every possible virus in windows xp is a hammer, or if you don't want to destroy your computer (fun as that might be) you could download a copy of Ubuntu, one of the easiest distributions of Linux to install and use that I've ever used. During the installation just tell it to format over you windows partition and all those viruses will be gone forever (more or less).