SOME ONE PAST MY FIRE WALL

[abanksob1]

recently my computer was hacked and i can see the person on my computer changing things ,how did he do this i have the up to dated fire wall and the new windows 7 i close down my computer and restarted it and hour later he was on it again...this is freaking me out how to get him off ? i am only on the computer for 30 minutes or so then i have to log of of internet when i see him on my descktop please help!!!!`