Best Free Antivirus for Home PC?

I have a Dell with Windows XP Home Edition. I had Norton Internet Security through my ISP, but it slowed my computer to a crawl in some cases. I got it removed, and I told my ISP to take it off my bill, and am now wondering what is the best Free or Free to Try, Antivirus protection. I tried Avira but it messed things up as well. AVG takes too long to install since I have dialup.