Its a lil more complicated then that, with 4 gigs vista needs to page more stuff out to the hard drive more often especially when yer running 5 games at once.
With 64 bit yeh get a performance hit from running emulation buts its made up by the fact yeh dont have to page out to hard drive as often because yeh have lots of memory.

Any time a computer has to page something out to the hard drive its a serious performance hit consider hard drives are an order of a magnitude slower then memory.

32bit emulator is limited to 4 gigs of memory no matter how yeh slice but the problems is that each apps is limited to 2 gigs unless it was specifically compile with /largeaddressaware then yeh need to use the /3gb switch to allow it to use 3 gigs of memory. One app= one instance of wow considering wow dosent use more the 500 megs this is a non issue.


Oh, and to crush a myth... World of Warcraft is a 32-bit game, so running it in a 64-bit operating system will not improve things. Even if you run 8Gb of RAM, the 32-bit emulator only seems about 3.2Gb of it. I got this from my computer builder who designed most of the systems many coal plants use here in SW Pennsylvania... unless you actually work for Microsoft, I'm going to take this guys 25+ years of expertise over anyone here.