> "Already, I'm confused. Which one of these versions allows me to use all 48 GB of my server's memory? ... Just try to make sense of it all. I dare you. No, I double dog dare you! "

Dare accepted. It's actually right there, 1 click away from the page Jeff linked to: http://www.microsoft.com/windowsserver2008/en/us/compare-spe...

The answer to his question is Enterprise, Datacenter, and HPC.