I recently purchased a network for my two computers and now I have a problem. I set both my hard drive and the other computer's to Full Access Sharing. I have it this way because I would like to have full access to the other computer from the other. But then yesterday, some dude installed a worm program onto my computer over the Internet, so now my access is set to Read Only. The worm is gone, but I would still like full access to the other computer without getting worms every time I get on the Internet. Will a firewall solve my problem? If so, could someone give a quick definition of what all a firewall does? (I have only a hazy clue of what a firewall is).

Thanks....