Sounds like for some reason your XP installed in "Standard PC" mode instead of ACPI.
Check your device manager, under "computer"... I'll bet it says "standard pc". It should say "ACPI PC"
Something in your system probably isn't ACPI compliant.
Check out the Anand FAQ about "Why are all my IRQ's the same in Win2k".
You sort of have the reverse problem, maybe try to do a reinstall like it says and force ACPI Pc instead.
Might want to see if there's an update for you motherboard BIOS or something first, that's the most
likely candidate.