2. swaped the ... power supply
I Still find it odd that windows 2000 was always ok.
As Charlie says, it's most likely a hardware thing - there are many SME6 & 7 users here not experiencing the problem.
I would suspect the power supply, because when you kick off a big copy task, the HDD would draw more current, which could cause a voltage to drop out of range on the motherboard. That's the most obvious thing that changes at your point of failure.
Can't really think why the WinXP is different from the Win2k.. Interesting.
David