Dear Forum Members,
I have 2 Motherboards that works very strangely.

[1.] MOTHERBOARD SPECIFICATIONS:
GenX P4M800-M Rev 1.03 Socket PGA 478
Processor : Intel Celeron D 2.26 GHz |256|553 SL78K MALAY Q540A642 0135
AMIBIOS 686 1999 TH43 7593 C 1.00 - 10A

Operating System: Windows 2000 Professional Edition
Memory Size: 128 MB DDR |333| CL 2.5

SYMPTOMS:
When the Pc is switched on, the Monitor goes on very briefly then the "[B]MONITOR IS NOT CONNECTED[/B]" appears on the Screen nothing else appears even POST Messages. I had to Change the RAM PC3200 256 MB DDR-DIMM CL 3 and worked for 1 month since then nothing seems to work anymore even by using the same 128 MB DDR |333| CL 2.5 and adding new Video cards.

[2.] MOTHERBOARD SPECIFICATIONS:
ASUS P2L97 Rev. 2.05
Processor : Intel Celeron 2 GHz |128|400 SL32A | 300A766
AWARD PCI/PNP 686 S/N 122505797 1998

Operating System: Windows 2000 Professional Edition
Memory Size: 192 MB DIMM

AMIBIOS 686 1999 TH43 7593 C 1.00 - 10A

Operating System: Windows 2000 Professional Edition
Memory Size: 128 MB DDR |333| CL 2.5

SYMPTOMS:
The Pc starts without power button being pressed to shut it down i have to disconnect the power cord from the Power Supply, the Monitor goes on very briefly then the "MONITOR IS NOT CONNECTED" appears on the Screen nothing else appears even POST Messages.

Can you please help me sort out these problems?. Your help is greatly appreciated.

Start with the last symptom first. You may have the case wiring connected wrong, your PSU may be defective or the MBoard may be shorting out on the case. I suggest you go back to square one.

Remove the MBoard from the case and check to verify you have the case standoff installed behind every screwhole in the board, and ONLY behind screwholes. Post back if your case doesn't use standoffs.