Connect two computers with internet and VPN connections

I am under a network with two routers with distinct IP address connected together. The first router is used for accessing internet while the other one is used for making VPN connection in other place. What do I need to do to allow a Windows 2000 or Windows XP PC to have access on both locations? That is for the internet and VPN. And also, I need the two gateways to be in a single port. Can someone please help?
