Uh oh's, is this getting into 32bit V 64bit now?
I will flat out state that the majority of people, ie the average PC user... even extending to "hardcore" gamers. Do not need anything more than a 32bit OS with 3GB of RAM (and yes, you can do a little tinkering in 32bit OS' to allow 3gb, I do believe it's even called the "3gb switch" in XP). Your GFX card will play a HUUUGE role in game performance.
However, for quite a small percentage of people... 64bit OS' and 64bit programs with butt-fuck loads of RAM is essential, especially for those of us who work on these machines at a professional level (and require something a little more hefty than Microsoft Word and Excel). I don't know what Eggo does for a living, or whether or not he's into some serious power/memory draining hobbies... but there's nothing wrong with having a machine so beastily powerful. And it's rather pointless to argue.
Yes, Vista 64 uses up a lot of RAM to begin with, but when you've got 8+ gigs in that bad boy, it really doesn't matter, 512 or less being used by the OS is no sweat, and you get the benefit of 64bit stability, as opposed to XP 64bit (which my main PC is currently on)... I've had a lot of problems with it, and I'd happily trade a few hundred more kb's of RAM in turn for a more stable OS, again... going back to the 'professional' point... some of us can't really afford unstable working environments.
Essentially... if you're looking to buy a PC, and you don't know whether or not you want 64bit... chances are you'll be perfectly fine with 32bit. There are not a great deal of games that are even made to 'take advantage' of 64bit systems either. A maxed out 32bit system will still handle HL2, Stalker, Crysis, Far Cry... can't actually think of anymore, very well. Especially HL2, Far Cry and Stalker... I'm unsure about Crysis, what with it being very memory intensive at full spec and needing DX10 too (again though, a bonus of Vista).
I'm starting to lose my train of thought here... typing over.
