Most likely due to the Core 2 Duo + 10k RPM Raptor + 2 Gig of Ram + Decent graphics card.

Try doing it with a single core processor, a gig of ram and 7200 rpm hard drive and playing 2 WoWs gets a bit more difficult / laggy.

Hmm..... so with a Quad Core... 5 Gigs of Ram and a DRAM based hard drive.... I could theoretically 5 box on 1 machine Not sure that I would want to though. There are still bottlenecks - plus less redundancy.