As far as I'm aware, number of processors and number of cores is two different issues.

e.g:

"A physical processor is a single chip that houses a collection of one or more cores. A core is a collection of one or more processor threads and a set of shared execution resources. A processor thread is the architectural state within a processor that tracks execution of a software program thread/task."

"Windows XP Professional can support up to two processors regardless of the number of cores on the processor."

http://www.microsoft.com/licensing/h...multicore.mspx