Hmm. . .strange that your Device Manager doesn't show your processor. When I first upgraded to XP, I thought it was strange to have it, but I wonder why yours doesn't show??.
You might try flashing your BIOS to the most recent version. Go to your motherboard website and see if they have an update for you.
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Try letting a friend that knows something about computers come over and look at your BIOS with you. I know that sometimes the numbers just get all jumbled together. I overlooked my clock speed settings several times jntil finally one day after about a month of wondering why my BIOS didn't have the settings, I looked right at it and slapped myself for not seeing it the first time. Mayabe a set of "fresh eyes" will be able to see the settings that you happen to be overlooking. (Just a suggestion.)
If they are for sure not their, maybe the updated BIOS will have them for you to set.
God bless,
Bobby