You can configure the VPN in different ways PC to PC, router to router, router to PC.
If you want to setup VPN for PC to PC take a look at these documents.
First you will need to configure the PC at home as a VPN server.
http://www.onecomputerguy.com/networking/xp_vpn_server.htm
Then configure the remote PC as a client.
http://www.windowsecurity.com/articles/Configure-VPN-Connection-Windows-XP.html
As for creating the VPN via PC to router your best bet is to go to the manufactures site and look for a PDF user guide which will show you the steps in configuring the VPN.
If you configure the VPN this way you will then be authenticating to the router so what ever details you enter into the routers VPN setup are the ones you must match.
One other thing you must configure port forwarding to all the connection to come into and pass through the router.