Can anyone tell me what are the latest virus-definitions for symantec and mcafee and where I can download them.

A lightweight AV is ClamAV, but that one is from 98 up and as Firewall you could use Sygate, i think old version will run on 95.

But I don't use AV or Firewall on old computers. Like DOS, W9x or W2K, I only do an file scan from time after time, which is very rarely. If a computer is not connected to the internet than a AV is not necessary. And new malicious software is not compatible whit an old OS like Windows 95 (win9x is not a target anymore), and the old viruses are mostly extinct on the internet (only if you have some old disks or CD that are be infected could become a problem and should be scanned).

So if you only play old games and all those games are scanned on another machine than you don't need a virus scanner. To be more secure you could disable the network card in Windows.