LAN Antivirus

Would anyone in the forum be able to provide me with some solutions for maintaining a "funk-free" (virus and worms) LAN from a RH 7.2 server? I have found some hardware that prevents the funk from entering the LAN at the firewall. But it's to pricey for my humble LAN of 7 windoze clients. Is there a package avaliable that would install on the RH sever and filter http & ftp traffic? I found several packages that filter email in the manner. I spoke with some ppl that suggested I just install a package on each client and the server, but I like the idea of keeping the funk from entering the LAN at all. Maybe I dont understand the technology as well as should. Could some please offer some advise on their experiences and/or solutions? Regards, Chris