PC won't turn on - lights and fans spin up for half a second

[chuckyrp]

I've got an old PC that has stopped booting up.

The motherboard (Asus P5LD2-VM) light lights up, the light on the card in the PCI1 slot lights up, the cpu fan and case fan spin up but it all only lasts for half a second then they all flicker off before coming back on again and the cycle repeats. It seems like something is shorting it out and then it tries to power up and fails and repeats.

I had a spare power supply so I tried replacing the power supply but the same problem occurs. I've tried disconnecting all the power cables and reconnecting multiple times. I've removed all of the peripherals, removed HDD, CD drive, cards in PCI slots and tried to boot with just CPU and Ram but I get the same result. I tried all of it outside of the case, same result.

Is there anything else I can try?

Thanks in advance for any suggestions.

 

[adiec]

try clearing cmos . Locate the round, flat, silver battery on the motherboard and carefully remove it. Wait five minutes before reseating the battery

do this whilst the system is powered off and the lead is removed from the back of the power supply unit .

 

[chuckyrp]

try clearing cmos . Locate the round, flat, silver battery on the motherboard and carefully remove it. Wait five minutes before reseating the battery

do this whilst the system is powered off and the lead is removed from the back of the power supply unit .

Should I replace the battery while i'm at it?

 

[adiec]

try clearing cmos . Locate the round, flat, silver battery on the motherboard and carefully remove it. Wait five minutes before reseating the battery

do this whilst the system is powered off and the lead is removed from the back of the power supply unit .

Should I replace the battery while i'm at it?

just put back the same battery that you removed .