Computer does not reconize the second processor.

Hoping someone could help in this problem while I wait for Dell help support to answer. Was advise by Dell Help Chat that my Hard Drive was bad. A contracted Dell service person installed a new Hard Drive that was pre-loaded by the factory. Soon there after I noticed that my computer was using only one processor.I have an Intel(R) Core(TM)2 6300 @1.86 HMz. Prior to the Hard Drive crash my computer was doing two units of work for SETI. Now it only does one unit of work.

Device Manager show two processors, Task manager shows only one processing. Any ideas?

Computer is an E520, Windows XP Media Center Edition, 1 GB RAM