In my experience, the only problem I've had is playing Diablo II multiplayer, because it sees it as installed in the 'wrong' folder, because any 32-bit native apps get installed in the 'Program Files (x86)' folder rather than vanilla 'Program Files'.

Other than that, all my older games run without a hitch in 64-bit Vista.  But the benefits of 64-bit seem too great to pass up for Diablo.

32 bit is best for playing older games but has less ram need to up grade. and turn off the useless back ground junk that vista runs that eat up cpu and ram. to tweek vista in start menu type service click on service in program box . note only turn off what you do not use double click selectd items you want to change and disable or pick another action i use 32bit system dualcore 2 gig of ram ati radion 4800 graf card can play just about any thing out there and also when tweeked vista loades20%faster and no longer crashes .

i run vista 64 bit and have had no problems playing sim city 4 or rctycoon 3 just make sure you have service pack 1

Unicatsins, there *are* games that can make use of 64 bit -- one of them being the upcoming Elemental: War of Magic.  I'm going to upgrade my desktop to 64 bit JUST for the larger maps made possible

Here is my tuppence (two cents) worth:

I am still on 32bit XP and have no problem running the software I want - games at decent frame rates at close to maximum settings with the highest resolution my monitor can support.  That is not to suggest this is how you should go - just to put what I have to say in the context of my experience.

Processors are not getting much faster - they are going 64bit and multi-core.

If you go Vista 64 bit (Ultimate) you are permitted to use the same DVD to set up a dual boot system, one 32 bit and one 64 bit.  so you might as well go 64 bit and only worry about dropping back to 32bit if you have a specific problem that you cannot overcome with a piece of software you can't live without.

I have Vista 64x and have no problem playing any of my older games. I can play everything from rollercoaster tycoon, to morrowind, to supreme commander, even Populous:TB, dungeon keeper 1 and Starcraft (but the main menu has a few colour probelms). So I would go for 32 bit. Especially if your rig has more than 2 gig ram. And strangely vista seems to play MOO2 better then XP as long as you copy in the missing direct x files.

64bit has better driver support. Even an old game like System Shock 2 worked on 64bit. The trouble is some games from the DOS era are 16-bit, and you can't run 16bit on a 64bit platform.

Dunno about 64bit but an NTFS hard drive is not capable of running dos programs. However DOSBox will stil let you run them.

64 bit is the future. Today's games are eating up memory like crazy as textures get larger and models get more detailed. For hyper-realistic games like Crysis, you're gonna need as much memory (both system and video) as you can spare.

Even games like GalCiv 2 and WoW are eating up memory like crazy as people keep demanding larger maps and longer draw distances. Huge worlds and large universes means lots of memory, even if it's not a game that pushes video cards to their limits!

The only major issue you'll encounter is if you plan on playing ancient DOS or Windows 3 games - but those can be played on a virtual machine or on an emulator. Truth be known, I started using DOSBox even in XP, as XP itself is missing 99% of what DOS games generally needed to run.

Yes, DOSBox should work. For Windows 3 games, Virtual PC should work.

In fact, Virtual PC is good for pretty much any game that really wants to use an older OS as long as the game doesn't require hardware 3D acceleration. Just be aware that virtual machines running Windows use a lot of memory and hard drive space.

Thanks for the info, guys. I'm still with a 32-bit XP (works fine), but I was toying with the idea of buying a new rig, in 2009. Thanks to this thread's great tech discussion, it will be a 64-bit Vista system. Like Ron Lugge, I would want to try those extremely vast maps Frogboy has promised for 64-bit users with a lot of RAM.

By the way, to run old DOS classics like Master of Orion ('93) and Master of Magic ('94), I prefer to use VDM Sound (rather than DOS Box). My computer still has an old "Sound Blaster Live!" card, and I have not succeeded to get the best quality of music with DOS Box, whereas the VDMS program launches those two games easily, with full sound.

Sorry to be off-topic, but I must admit that playing the old Master of Orion today has little interest when you have extremely advanced games like Twilight of the Arnor. 

Yep. Absolutely...

I think you'll find that it is more of an "ain't broke don't fix it scenario" mate. And that "all the money in the world" is pretty much the bottom line.

Vista itself, although n00b friendly to the point of making things difficult, is incredibly stable. It's so helpful in fact that it has made me care a lot less about knowing how everything works. In fact, it's running my errands right now...everytime I think to complain it just sits me down in front of some game and then...wait a minute...