Agreed with above. You must have an antimalware program. Why is simple. Make one mestake one time, and you will end up with a machine so drowned in malware that it can hardly move.
If you think that I am lying, then I recommend that you look at my profile page.
Also, someone else that I helped had 126 infected files. That was last week. Do not underestimate the people that wish to harm you. EVER
EDIT: That person last week was not on this forum... I should have said that.