XP is a single processor that ocassionally is able to run in a dual configuration. MP is tested to make sure it can. They are two different processors. You will need to run some version of NT (2k, XP) to make both work. Most games are not able to access both processors, but some can, and many other programs can. The games that can't use the second processor won't even know it's there. Any problems you may have with the system will probably be unrelated to the number of processors it has.
What's the frequency, Kenneth?