Can anyone please help me?

I have Vista by the way. My computer recently became infected with a virus(I am pretty sure it was a trojan). So I did a full system recovery(press F11 at startup). So is it still possible to have that virus at startup? Also, what are some good antivirus programs? Free antivirus programs would be great. Thanks, help is appreciated.

OK thanks for the antivirus info. Can anyone answer my other question? Will I still have that virus after doing system recovery? Thanks for helping.