Hey,
I've had this problem too. If all your other performance counters are there, you probably have the right components. Make sure you have this DLL: perfos.dll
This is a problem with XP Professional too if you don't have a pagefile (virtual memory) setup. So options are:
1. Setup a page file, even 2MB will be enough, reboot. Use the Microsoft Extensible Performance Counter List tool: http://www.microsoft.com/downloads/details.aspx?familyid=7ff99683-b7ec-4da6-92ab-793193604ba4&displaylang=en
and select Performance Counters Enabled on the perfos.dll Service. Click Refresh and it should stay now that you have a page file. You can check perfmon and the processor counter should be there.
2. If you can't have a page file, you will have to deploy the image again. You'll have to request a file from MS. On the first boot run this patch: http://support.microsoft.com/?kbid=884558
This will keep the performance counters there without having a page file present.
Good Luck,
Michael