Help with antivirus xp 2008??!!?

yeah my computer, my dear computer, got infected. i tried to get rid of it manually but its so hard and long. i turned to anti-virus programs but some require me to pay and i was actually on the brink of purchasing "SpyNoMore" but people said it was also "rogue-like" and i definitely do not want to go thorugh it again. help me!! suggest a anti-virus program, or anything. if i have to pay i would but i have to know if its legit and worth it.