I have a machine with XP Pro SP3, on an Asus P5L...something board and an Intel E5200 dual core CPU.
The BIOS shows both cores, and windows shows both cores in device manager, but not in Task Manager.
See screenshot: http://edgebox.ca/singlecore.PNG
From what I've googled, it seems to be a problem with the HAL ACPI thing, needs to be a multiprocessor one, but I don't know how to switch it?

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