NT 4.0 and W2000 HAL Multiproc are completely different. If you are in W2000 and want to upgrade to another proc. do this: To go to multiprocessor, the Processors have to be the same size/speed/stepping. Look on top of your processor, it has a whitish grey stamp on top which should have the speed/size of cache/stepping on processor for example: 80523PY350512PE SL2U3
The 350 after the PY is my speed the 512 is my cache and the SL2 is my stepping on the processor. Make sure you have the same speed/cache and try to have a stepping that is only one number off or the same anything else won't work.
Now for the Processor Upgrade this is how to approach it: 1.Upgrade the system BIOS Firmware 2.Go to F10 and go to Advanced Mode by pressing(Ctrl+A) GO to Sys config>Advanced Mode> View and edit details>Advanced Features>APIC-Full Table> Save and Exit. 3. Down the server. 4. Add the second proc. 5. Get on to W2000 and then go to My comp>Manage>device Manager>Press+by my comp>ACPI>Driver>update driver>NEXT (Wizard)> Display a list>Pick ACPI Multiprocessor>Enter and youre done.