We have a Windows Server 2003 machine running as a VM on top of VMWare ESX 4. That VM needed more CPU power, so I powered down the VM, added a virtual CPU and restarted the VM. If I go to Computer Management -> Device Manager, in Processors I see two processors, and in Computer, the kernel is ACPI Multiprocessor PC, so far so good.
Problem is: Task Manager only show one CPU and we are also monitoring CPU usage with Nagios and we still get 100% CPU usage at times, but the VMWare console show that the CPU is using 50%.
So it look like parts of Windows thinks that it have only one CPU even if other parts thinks it have two CPUs.
After doing somme Google searchs, most of the time the problem was that the wrong kernel was loaded, but