The cheap option would be a Nix Server something like SUSE Server but will they have the money for a Server firstly or at the very least a Desktop unit that no one uses directly?
Also depending on your Skill Set this may not be an option or depending on what it is that they do it may not be an option.
If they will not exceed 10 users and 1 Network Printer Windows Server 2008 SBS will work though you'll need to buy an additional 10 CAL's to give you some room to grow on top of the Server Application. It also depends if that have any Mission Critical Applications if they do you'll need to get a OS that that Application will actually run on. [i]A 10 User Cal's Pack is cheaper to buy than 1 X 5 Pack and a Single CAL.[/i]
But firstly do they even need a server? with 10 Systems they could use a P2P Workgroup running whatever version of Windows Desktop suits their needs. Though if you are considering using 7 you'll need a version that can be connected to a Domain so that either Enterprise or Ultimate. Enterprise is the Volume License version of Ultimate to all intents and purposes geared to a Business Application. And then with Modern Hardware capabilities it should be a 64 Bit OS.
If they need to use a OS like XP it will need to be Pro and ideally the 64 Bit version but that may very well require some very selective Hardware Selection so that you can actually get the drivers for that OS.
Col
