My friend, stop with the warez hehehe . Nah but serously if you have a 20gb HD, partition it into like 2 - 4GB and the other half 16 - 18GB depending on how you wish to divide. Lets say you choose 4gb. You'd have 4gb and 16gb. 16GB would be for Windows and 4gb would be for linux or BSD. THis way you dont have to overload your gateway server. ALso, shouldnt gateway server be on 24/7 ? so your other systems can access the net. So let me know if this works for you. ALso, if you have like $65 you can get a new HD.

Just remembered, Hardware firewall? No offense but I think he should first get a hang of networking and then go into that. Mantis get a ZoneALarm or Black Ice both are free, pretty good software firewalls and when configured properly, they'll stop most minor attacks.