I just replaced my P4 1.6 with a new 2.8 "C" Gig HT P4 800 mhz CPU and experienced problems from the get go. I think the problem is my Asus P4S800 mb. The support page says it should support this cpu. When i first installed the CPU, win XP Pro hung on boot up and the bios stated that cpu speed was wrong. I removed the cpu, put the old one in again (ran fine) and used EZFlash to Flash the bios to the latest P4S800_7. Reinstalled the 2.8 CPU and now it will boot up ok. BUT... when I go into Device Manger under Processors there are 2 CPU's listed. If I try to uninstall one it reappears on next boot-up. More seriously, when I tried Sisoft Sandra Standard and PCMark2002, both benchmarks confirm that the cpu is only running at 1.4 Gig. I checked the bios again, it says the cpu speed is 2800 (14x multiplier and ext. freq of 200/33). Why is the bios saying one thing but the cpu is actually only at 1.4 Gig (half speed)? And why are 2 prcessors showing up in Device Manager. Do I have to manually change settings or jumpers? nothing in the manual? Any help appreciated. Thanks.