I don't think the Prescott CPU is compatible P4 Prescotts require a 800MHz FSB. Yours is currently running a 400MHz FSB. Being a 1.5GHz Compaq this is probably about 2-3 years old and I believe you might be stuck with a 2.2GHz CPU running 400MHz FSB cap with your MB. You might want to download Everest to see what chipset your MB has then you can research to set what the maximum CPU speed that will run with that particular chipset.
http://www.snapfiles.com/get/everest.html