I need help, which vpn solution is best?

I work in an office of 15 people which has a win nt 4.0 server and i need to conect to our other office of 5 people which also has a win nt 4.0 server(they may get upgraded to server 2003). I have never setup a VPN and would like some sugestions on how to do it and what would be the best cost effective solution. Both offices are on ADSL and curently conect with GOTOMYPC.com Any help would be greatly apreciate it.