Forcing Windows XP multicore detection

Recently I had to resume a Windows XP Virtualbox VM, to do some tests.

I have added some RAM and CPUs (from 1 to 2) to the VM, but the added CPUs aren’t detected.


After some internet surfing, I found the solution.

To force the detection, open the Command Prompt and type the following line:

rundll32 syssetup,SetupInfObjectInstallAction ACPIAPIC_MP_HAL 128 %windir%\inf\hal.inf

After a couple (in my case) the system will detect correctly the newly added CPUs.