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It depends what you want to do, but Home Premium is probably what you're looking for. Unless you want Vista only apps, I strongly recommend XP Pro :)
 
It depends what you want to do, but Home Premium is probably what you're looking for. Unless you want Vista only apps, I strongly recommend XP Pro :)

Why do you recommend xp over vista? and should I be getting the 64-bit version of the operating systems? or will the 32-bit be fine with the mac pro.

for a bit of information I plan to run a few games on it.. like half life 2
 
...and should I be getting the 64-bit version of the operating systems?
You will almost certainly want to stay clear of the 64-bit version because of the lack of 64-bit drivers. Also, the performance bump for 64-bit over 32-bit on CD/C2D is only about 10%, with essentially all of that coming from floating point operations.
 
Why do you recommend xp over vista?

1. Its much cheaper
2. A lot less buggy - it has gone through two service packs
3. Runs a bit faster
4. Quite a few apps don't work (properly) yet with Vista
 
Unless you need/want to connect to a domain, go with Vista Home Premium. It has all of the eye candy, has Windows Media Center, has the pretty photo gallery and DVD maker, and the scheduled backups function.

XP has none of these things.

Ultimate and business have some features, such as: encryption and domains, which you will most likely never use.
 
For Vista, Get Home Premium or Ultimate if your budget allows. (32-bit)
For the Most compatibility, Get XP Professional 32-bit
For a balance between compatibility and speed, get Windows 2000.
For a glance at why you chose a mac to begin with, Get Windows ME. ;)
 
If you're absolutely uninterested in ever using vmware fusion or parallels desktop, I say home premium 32 bit.

32 because 64 won't have the driver availability for quite a while now; you'll notice that extremely few organizations would use 64 at this point nomatter if their hardware is 64 capable (thank you apple for not ***** up leopard with 32/64 BS!). 64 will not offer tremendous speed jumps either.

I say Vista instead of XP not because it's more reliable or easier to work with at this point (it's not), but because you'll be glad you bought vista in a year when it's at SP1 and is pretty much the norm. bootcamp parallels etc. support vista, so why not.

If you might ever be interested in virtualization, you technically need at least vista business. The OEM of business (the catch of OEM is that you can only ever install it on 1 machine (in theory at least) and that you don't get support from microsoft....HA!) is about $150.
 
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