If you've reformatted there is a pretty good chance that everything is ok... i may be naive but i'm pretty sure that a backdoor could not hide in a bootsector. However if you are still paranoid you could always go through your registry and look for suspicious entries. I mean if the person coded it themselves you really are kinda on your own as far as AV's go.... HOWEVER... what I and everyone else that's going to reply would strongly recomend is a FIREWALL. I'm sure someone will give a list of decent ones... I would but I don't want to point you in the wrong direction... hope this helps.