cmi86 :
E6600. Yes. Q6600, No. This boards supports a maximum of core2 duo family. Here is the technical information page on your motherboard from HP.
http://h10025.www1.hp.com/ewfrf/wc/document?docname=c00864946&tmp_track_link=ot_recdoc/c00837320/en_us/c00864946/loc:1&lc=en&dlc=en&cc=us&product=3340228
the CPU I'm trying to use is the Intel® Pentium® Processor E6600
(2M Cache, 3.06 GHz, 1066 FSB) - when I install it get a blank screen, but PC boots normal with the E6300 back in - wondering if a bios update is needed to recognize the new CPU? - thanks