Allan I am sorry this isn't going to help you I seem to be having a similiar issue.
This post is a long one sorry.
I have -
GA7ZM E148299 – AMD 850 mghz
MAXTOR 2F040L0 HARD DRIVE 38 G
NVIDIA GEFORCE4 MX 440 VIDEO CARD
ONBOARD SOUND
NETGEAR NETWORK ADAPTER CARD
CDROM CREATIVE CD820E.1V0789108
CDWRITER SAMSUNG 48 – 24 - 48
WINDOWS XP PROFESSIONAL
OFFICE XP PROFESSIONAL
that I built, when I put it all together it booted fine to install O/S however after installing everything I needed I noticed the HD and Power lights weren't on I figured I have the wires backwards so I turned them around so pin 1 was at hole 1 when booting the system appears to start, the fans turn on all the lights come on blink or what ever they are supposed to do in a normal boot. The monitor stays blank no post no beeps nothing then the hard drive light goes out. If I hit the reset button it boots fine. I have switched every component in the system including the power supply and the same thing happens until I took everything out and changed cases, at which point it booted fine about 30 maybe 40 times. The case I put it in was already sold to a customer so I had to take it out of that case and bought a new case, I put everything into the new case it booted fine about 4 times when I noticed the lights on the front weren't on. Again I had the wires turned around changed the wires no boot no post no beeps but the lights and fans come on hitting the reset button boots it. Turned the wires back the wrong way and it still isn't working. Took battery out, flashed bios, still not working. When I took the battery out - the first time I power it up it comes on with an error to enter setup or load defaults either way I go it boots but to power it down then start up again the same thing happens. The MB was given to me with the CPU. I imagine they couldn't figure out why it wouldn't boot right.