Something like this
rack.jpg
Looking for Xeon 5660, Power supply and Graphics onboard. Most of them have a few hard drives and a lot of fans.
Is there any reason why this should not run like a single PC ?
It should run similar to a normal PC. However if you use Windows, you cannot use any Basic, Starter or Home editions. Your only options are Professional and Ultimate. The other versions will not support 2 CPUs.