two networks on one machine

[snook123]

hi guys can you help im running xp iv got two network cards in one machine how do i set up two differnet networks with a seperate internet connection on each network but only use one for(example server pc on wired network with internet 1 nic second nic on different wired network with wirless also and a seperate internet ie two modems one for each network but i want each machine on the differnt networks to access data from the server pc) (hope this is clear?) dont think there is a wizzard for this so gonna have to do it manually i think. i get the idea that you have differnet gateways but how does windows programs know wich network to use for the internet and how does each machine on each network know which internet connection to use becuase clever xp sees both modems and picks what ever it likes? HELP Cheers