Need advice on remote access

I have a small business and have a network setup as follows:
4 workstations running WinXP Pro.
1 computer serving as a "server" to the workstations running WinXP Pro.
I have a dedicated IP address thru Sprint DSL.
The "server" is not running as a true server as I understand it. I currently have no problems at all with this setup. My problem is that my main software for the office is called "Agency Advantage ", a program for Insurance agencies, that keeps track of policies and customers. This is a very slick piece of software and I love it. However, I have two offices located about 15 miles from the main office and I need these two to have access online to the program and I am in need of advice on how to allow them access. Is there a way??

 

If both ends of each office has a static IP, you can build a branch VPN tunnel between the two to connect to each other through the Internet.

Linksys and Netgear carry these products. I would suggest a higher model of Netopia though.

Once you build the branch tunnel, it is like a private WAN circuit from office to the next. And if you have a pretty decent one at your core office, all 3 offices are considered interconnected to each other.