Networking Distant Computers?

I am trying to network two offices that are 150 miles apart. I have been told to use a VPN router to best accomplish this but I am not sure how I can do this. In my new office there is only 1 computer at the second, and it has a static ip address on a cable modem. My main office has 3 computers networked together sharing a cable modem. I need to be able to set up a Map drive from my server in my main office that can be used by a program in my new office. Please email me with any specifics you need to give a best answer. Thanks!

Two easy options for you.
One http://www.hamachi.cc/
a software VPN client that will allow you to create a logical VPN connection from PC to PC
Second
Buy two Linksys RVL200 VPN routers.
Replace the router servicing the 3 computers and put the second single machine behind one of these. Once you set these up via the web GUI they will automatically VPN to each other and all the machines should see each other like they were in the same room. This is nice because you can add and remove machines with very little configuration or setup. Secondly this is the fast of the two options since the router does all the encryption and decryptions.

Caviats!: You IP address may change, unless you are paying for static IP address from your ISP. If this happens the tunnel will be broken because each RVL200 needs to know the distant end IP address of each other.

Basically the way to accomplish what you ask is:
1. Set up a VPN connecting the two sites. This requires setting up a 'Certificate Authority' on your server so that it will be able to use a digital ID, setting up a VPN server program on the server and configure the remote computer to connect to it. This will join your remote computer to the main office network. Anything you can do locally, you will be able to do from the remote site, only slower.
2. If the only purpose is running programs residing on the server, the better way would be to connect as a remote desktop client. This way, no files are transferred, only screen images and keyboard/mouse information. The connection will work faster, but the data will stay at the main office (ie, if your communications shut down, the remote side has nothing).