this is a real point of confusion -- the socket p and socket m mobile chipsets are 478-pin, and take the T5000 and T7000 lines of processors, and are incorrectly labeled as "socket 478" by resellers instead of socket p and socket m. as far as i know, there is no compatibility between the desktop socket 478 (celeron/pentium 4) and the mobile-specific 478-pin socket m and socket p c2d processors. frag may have more insight, though.
sorry to be a debbie downer! :'(