I dont think anyone would use it. That is for high end machines with multiple CPU's and such. Just like a DataCenter.
Windows HPC Server 2008 can efficiently scale to thousands of processing cores and provides a comprehensive set of deployment, administration, and monitoring tools that are easy to deploy, manage, and integrate with your existing infrastructure.
Nope. You will be jsut fine with Enterprise or Standard edition of Server 08. Even Vista will be just fine for you. It can handle Dual Core just fine. XP can handle Dual Core.