Just thought I'd share my frustration (and solution) of the last few days.
My home built Asus P6T Intel I7 system would not shut down. Every time it would appear to shut down normaly and then start right up again. To make a long story short... after a few days of searching and trying many many many solutions I final found a suggestion to reset the CMOS. (done by moving a jumper) and voila it worked. (it never dawned on me this would be needed on a brand new system)
No doubt most of you know this but next time I build a PC the first thing I'll be doing is resetting the CMOS