I would still need a rough budget to give you a good spec for the price, with everything I listed above still being relevant, including the CPU, amount of ram, HD etc..
For graphics card - Games are slowly starting to gain support for DirectX 10, so it is a good idea to buy a card that does support it. Some new games will already improve the graphics if such a card is detected.
At the moment I would recommend the nVidia 8800 GTS. It's not a cheap card but as you want to be able to play the latest games the graphics card is going to be a central part of your new PC. The GTS is a cut down version of the 8800 GTX and Ultra versions, and is currently the best card for the price. And with Vista it will run all DX10 games very well.
And regarding the OS. I would recommend you do now get Vista as the first Service Pack is due out at the end of this year and will fix all the current known bugs in the new OS. But I mainly recommend it because games in the coming year are going to start requiring Vista to take full advantage of the hardware because DX10 is Vista only, so running in XP will run the games in DX9 mode.
The best solution at the moment is to install XP and Vista on the new PC, so you have the best of both OSs. It's not hard to set this up. You just need to partition the HD with a partition for each OS and a third for the remaining space for files. Install XP onto the first C partition, then once complete install Vista to the next D partition, and then you have a boot menu when you turn the PC on and can boot into each OS. Each and for older games running them in XP is a much better solution than trying to get them to run in Vista.
Finally as I already said, if you give me a rough total price I will make you a list of compatible components for the price.
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Oh shit, I forget one of the most important questions.
Sorry about that, well I had around 1000 Euro - 1200 Euro in mind, but then I would expect a machine I could use for at least two years before I have to upgrade again.
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