weird new build problem - arghh

[che1]

When i power on my system everything powers up ok, but when it comes to post the internal speaker goes off like an ambulance. I can enter bios, see the post screen where i get "cmos checksum error" and if i press F1 with my hard drive attached i can even get into windows, but as soon as i reboot i need to clear cmos because the screen blanks out.

I've tried switching the memory around, using a different PSU, running the rig outside of the case and changing as many bios settings i can which could possible result in this prob.

My Setup:
Abit KN9 nForce 570 Ultra
Leadtek GeForce 7300 GT
AMD Athlon 64 3800+ 2.4GHz
GeiL 1GB PC6400
Jeantec 450W PSU

Any help would be much appreciated cuss im well stuck!

 

[che1]

all my temps and voltages are fine in bios.

and yeh its kinda like a siren. My heatsink is fanless so there is nothing plugged into the cpu fan pwr plug.

and yeah i tried replacing the cmos bat, still the same.

 

[che1]

its got a strange 4 pin socket on it, which i dont have. but surely that wouldnt cause such problems?