Go into Device Manager, select Computer and then select the next Device which will
have ACPI somewhere in it. Click on Update driver and Select One, then choose Standard
PC.
When I do that, I get this:
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and when I click
Update Drivers, it asks for an installation CD - would that be the Windows XP CD? I'd like to find out what the actual problem is, and why, before I launch into unchartered territory with the Windows CD!

I should add, that Windows loads fine, and when I click OK to the error message, there are no ill effects, and everything seems to be running smoothly.