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Socket 939 should provide upgrading options for the next year or two (maybe three) so you should be somewhat fine as for upgradability. I wouldn't recommend the use of any ULTRA PSU - they are known to fail quickly. Maximum PC did a review on them a few months ago and it fell far short on many tests.
Yes, those parts
should be compatible with WinXP-64 Pro, but remember drivers - it's software you need to be more worried about. Drivers need to be specifically written for 64-bit operating code, which many companies are still getting at. I know ATI has 64-bit drivers (not sure about the AIW series) but you may want to check on the other components.
Hope that helps,
kram
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