First off, I'm not a sys admin. I'm just a software developer trying to help out my parents' small business.

Right now they have one server, a domain controller with a P4 processor running SBS 2003. They also have this machine hosting QuickBooks, MySQL for the old version of an app, and SQL Server 2008 Express for the new version of the app (which will replace the old eventually). They've been complaining about the workstations being slow so I figured it might help if they bought a new server and moved QuickBooks, MySQL, and SQL Server to the new server, leaving the old server as just a DC.

In trying to pick an operating system for their new server, I was thinking about Windows SBS 2008 Standard with enough licenses for seven machines. But that's a lot more money than they're going to want to spend.

So then I wondered if there's any real advantage to having a server OS as opposed to just throwing Windows 7 on the new server. It's a lot cheaper and I can't think of any SBS features that it would need if it's just hosting QuickBooks, MySQL, and SQL Server.

Would it be okay to use Windows 7 for a server like this? Are there any advantages to using SBS 2008 that I would be missing out on? Any additional tips are much appreciated!