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especially ... arey you on any network, perhaps mapped drives are not available, any non-standard storage devices ?, disabling anti-virus software ?

you have to try totally different (diff. speed, manufacturer, generally better) ask your friends to borrow you some mem. modules to find out what Windows XP likes on your mobo.
if you reinstall on...

I've seen this many (at least 5) times on different systems and was able to fix it every single time. It was always a minor incompatibility of the motherboard and the memory modules. Try using...