I'm having a problem on both of my computers. help please?

[Derdab]

My computer has had a horrible virus for at least a week. Instead of taking it to a repair shop, my dad bought me mcafee. Today I installed it and it took about 6 hours. But now when I type in my password for my profile, it acts like it will log me in but then it goes back to the log in screen where the different profiles are listed. I have windows xp. What should I do I'm starting to lose hope. unlock iphone 3g