Remote networking

I am wanting to remote network our 2 branch offices. All of the offices have a Windows NT 4.0 file server running. The officed are connected to the internet through DSL or cable. How can I get my workstation to connect to the other networks through the firewall/router then be able to control their workstation? I have done some searching and found programs that allow me to control other workstations locally, but I havent found one that allows me to get out through the internet and back into the other offices.

Thanks for any help

Jon