I'd second Worldwalker's suggestion of getting
AVG - my partner has
the free version on his PC and I have a paid subscription (because my work involves sending out files to clients and I
don't want to find I sent out an infected file by accident!
) So far, I haven't had a single infection, and the only problems my partner has had that AVG couldn't clean itself turned out to be malware rather than a virus as such (which
Malwarebytes' Anti-Malware program cleaned beautifully).