Originally Posted by BP
I'd wait until January and get an OEM copy of Vista with a new PC.
One thing I'd mention about this is right now with XP you need a minimum of 512mb memory and 1gig for the current top-end games. Generally, Vista recommendations on-line are 1gig for the operating system so you'd be realistically looking at 2gig(as 1 1/2 is an odd amount) for current top-end games. Either plan on buying extra memory or stick with XP for the next year. I for one will not be in a hurry to mass-beta test Windows newest incarnation. Get yourself a cheap copy of XP Pro on ebay and upgrade to sp2. Everything out there is designed for XP so you will not be behind the curve until the mainstream converts to Vista. Again, you probably have a year.
By the way, make sure that your decisions are forward thinking. For instance, buy a SLI mobo(allows dual video cards if identical) and a brand-name, quality, higher-end video card from the likes of Leadtek(6600gt/6800gt or better) or such so that when it comes time to boost the system you can get another identical video card and extend your pc's useful lifespan on the cheap(price will have come down drastically as tech moves forward). Even if you do not get a dual core processor, make sure the mobo supports it so you can upgrade later. FYI - not only is AMD the gamers choice for processors, its also a better value than Intel. Generally, an AMD chip advertised as 3000+ means although it runs slower clock speeds(2.4 ghz or so..) than it's intel counterpart, it performs similarly to 3.0ghz. 3000=3.0 intel, 3500=3.5 intel, etc...
Also, AMD and Intel have slimmed-down value processors and full featured processors at the same speeds so make sure to buy the higher end one. For example, Intel has Celeron and Pentium lines of similar speeds. Celeron is good for those who want to surf the web and type in Word but Pentium is the workhorse for more agressive applications. I'd recommend an AMD Athlon 64 or 64 dual-core. If you go the cost effective route, I'd get a 3800+ Athlon 64($100 newegg) and then you can upgrade later when needed. If money allows, you could go with this - AMD Athlon 64 FX-55 2.6GHz Socket 939 $189 - it was designed for 3d gaming and would fly.
For an AMD chip, you want to go with a socket 939 mobo or the new am2 socket that uses ddr2(costs more but somewhat faster).