How do i get rid of a virus?

i have 2 virus that i can not get rid of i have tried virus scans and everthing i can think of it in my windows system32 folder i have tried renaming them and i tried movin them it wont let me do anything what should i do plz help i have never had this problem before and i just redid windows to i download the rong thing on limewire and now it wont let me do anythig my cpu is running so slow plz help