There are 3 versions you have to determine -
[ol 1]
[li]The O/S on your workstations. It sounds like they're CE, but CE4 or CE6? Boot one up and you'll see it on the splash screen. CE6 is good for a few years, but CE4 is going end of life later this year or early next year.[/li]
[li]The O/S on your server. You need to be on Windows 7 or 2008.[/li]
[li]The 3700 version. Open any Micros application, click Help and About. That will show you the version.[/li]
[/ol]
I'm assuming this system didn't come from a dealership. Did anybody explain the licensing to you?