so you would say that the difference i would experience by having vista is pretty much nil?

XP is fine unless you really want DirectX 10, which isn't that important. Even in Crysis, where you can't use the highest settings without DX10, you can tweak the settings so it'll be virtually impossible to notice the difference between DX9 and DX10. (And Crysis on those settings WILL take quite a PC anyway) Also, Vista will be replaced by Windows 7 pretty soon (well, not sure when it's going to be released but I think it's soon?) which ought to be better. Right now XP is your choice, in the near future it's POSSIBLY Windows 7.

XP and Vista are like two fat Italian bakers who offer you a deal based on bread;

XP says that if you run errands for him he'll give you 10 breads every month!

Vista says he'll give you 13 breads every month for doing the same for him!!

When bread dealing day arrives (usually a wednesday) it appears that baker Vista intends to eat three of those, loudly, in front of you every month while XP lets you keep all of them.

So, on paper Vista is a fabulous baker and pal and yields more bread but in the real world XP will give you the same while Vista gets fatter (from eating your memory).

In conclusion; if ever you go to an Italian baker, don't buy shit from him if his name is Vista. And also; don't get Vista, use XP with SP3 (which helps a great deal) and wait for Windows 7 like the rest of us!

http://www.firingsquad.com/hardware/windows_7_gaming_performance/page6.asp

Heres some data, it performs better, worse or the same depending on the game.

Btw, using ram isn't a crime.

@Bugrimmer: What are your target specs?

Using RAM is not a crime, no, but using as much as Vista is a tad overkill when viewed in context with the actual performance and overall features of the OS itself. Kinda like fast cars; the last one I had actually got better mileage after I bumped up the power output because it worked more efficently and effortlessly.
I don't really hate Vista entirely but it did not deliver what it promised; a Windows especially designed for gaming that would yield significant performance advantages over (the now venerable, in sw terms) Windows XP.

my target specs are sorta top of the line, so memory usage isn't exactly a problem whether is be xp or vista. the only question i have right now is if the difference between xp and vista is big enough to justify a vista purchase. i need a concrete answer in like 12 hours coz that's when i'm gonna finalize my purchase.

Get Vista. It's slower than XP but hardware is so cheap that you won't notice as long as you have a decent graphics card and a CPU from 2006 on not called "Atom".

YOU CAN'T RUN DX10 on XP. Don't tell me "Alky project" because the project is dead and doesn't actually work in the real world. Even Wined3d has a better DX10 than Alky.

Also, you're going to be stuck whatever you do eventually because you won't have DX11 hardware.

will vista support directx 11 or higher though?

i'm going to get my computer in 8 hours. i need a definite answer. xp or vista? i don't care about memory usage or whatever. i care about cost effectiveness. xp is obviously cheaper than vista, but will having vista give me enough performance to ignore the cost?

Get Vista, with 3 to 4 GB of Ram you wont notice major performance drops. Vista also has better 64 bit driver support than XP. It supports DX 10, and will definately support DX11 (and 12, maybe even 13). Vista will also be around and relevant for at least 6 years. XP is good but'll be phased out snon, 7 is too far away (for you), get Vista.

Not sure why the rush to buy your OS immediately, but if that's the case stick with an X64 OS and go with an OEM copy of Vista 64 for under $100.

OEM Home Premium 64 has all the media center functions which are actually quite decent.

You're going to be installing over 3GB of RAM, possibly more in the future (RAM is cheap), depending on what else you want to use your system for, making any 32bit OS a dead end.

I really don't see the point in paying for XP, which is going to see its support cut once Windows 7 is released.

If you're starting from scratch (ie, buying a new copy of Windows and building a good hardware system) there aren't any real advantages to using XP64 since you presumably don't have any attachment to it.