I can't add much to this beyond what has been said but I will make a couple of comments about specifics:
1. Intel vs. AMD
Take your pick. Classic non-conformists like AMD because they're the little guy. I have always been satisfied with Intel processors, although all things being equal, an AMD with the same clock speed as an Intel processor costs less (the price of motherboards for each is about the same). Go with whatever one you can get a better deal on.
A note about the differences in cooling: If you believe that cooling is going to be an issue in your computer, plan ahead and buy a couple of extra cooling fans for your computer. Check out Mr Flibble's
CPU temperature thread over on the tech support forum for some comments about keeping the temperatures in your machine down. AMD processors run a little bit hotter than Intel processors, but not to the point where they will overheat under normal use on a more frequent basis than an Intel-based system.
@Rob-hin:
AMD's latest line of processors, the Athlon XPs derive their names from the claim that they deliver the same amount of performance as an Intel with a higher clock speed. For instance, AMD says their Athlon 1900+ processor matches the benchmark performance of an Intel 1900 MHz CPU even though the Athlon's actual clock speed is something in the neighbourhood of 1.6 GHz. You might check with a resource like
Tom's Hardware for some more information about these claims and whether or not it's true.
2. Motherboard
I had an ECS motherboard in an old Celeron 500 machine and I never had a problem with it. I've also had good experiences with Soyo and Epox boards. Most of the other name brands (Asus, Abit, Gigabyte, Shuttle, Intel, etc.) also put out good hardware and have good driver support. Again, take your pick.
If you're into gaming, one thing I'd advise you to do is avoid onboard components. Each of these is not only something else to break, but is one more thing to drain system resources. If you put expansion cards in for all of you major components (video, audio, network card, SCSI, etc.) you will be saving processor power for actual computing instead of "menial" tasks. I try to buy only boards with ports on them (parallel, serial, USB, PS/2) and not components.
Onboard video is the worst; make sure you have at least a 4X AGP slot and get a good video card. Not only is most onboard video of low quality, it often uses system RAM instead of DDR or dedicated video RAM. Plus, I've found it's hard to turn off if you decide later to upgrade to a higher quality video card. Onboard sound also uses system RAM and system CPU power, but not as much as video. Still, since you can get a fairly good quality sound card for about $50 (USD), there's no reason to have to settle for onboard AC97 sound.
Most full-size ATX motherboards will have an AGP slot and six PCI slots which should be more than enough for your needs.
3. RAM
RAM is like gasoline in your car; you can never have enough. If you have too much, that's great, but if you don't have enough, you'll sure as hell want more. Buy however much you can afford.
4. Price
A lot of people go about buying a computer the wrong way. Instead of listing the features you want and then buying a computer with those components, you should figure out how much you can afford to spend, and then buy the best machine you can get at that price. Any computer you buy
will be obsolete the day you purchase it, so suck up the depreciation and get the most bang for your buck.
5. European websites
Sadly, I don't know about buying computers or components overseas, but Mr Sleep and others might.
If you fill out their questionnaire, they will give you a 5% courtesy discount. 
) I will simply say that I went with an Athalon system based on my research and wanting to support the "underdog". I chose the A7V333 Athalon motherboard because it was one of the few motherboards at the time that would support the Corsair 2700 CAS 2.0 RAM I wanted (actually, I wanted the 3000 but there was no support for it at the time). I went with 1 GB with RAM on a WinXP machine and have not been sorry, though the tech who built my system said that the 20% performance boost probably wasn't all that noticeable. I would recommend a GeForce4 TI4400 video card, which is comparable to the 4600 but less expensive. Also, I am very happy with the Western Digital Caviar SE 100 GB hard drive... all of these components have contributed to a very fast and responsive machine. If you are creating a system from scratch, an unglamorous but important consideration is the power source. Enermax is a good choice. 
and what pixel and vertex shaders were. 
Linear Mode
