1.when i tried to start my pc yesterday morning , it refused to start.

2. I checked the power supply (SMPS)light. When i start the main switch, this light and fan starts for a few seconds and again goes off.

3. But when i disconnect the pin which connects power supply (smps) to motherboard , the light remains on. Does this mean that the power supply is working fine but the motherboard has problem.

4.My pc refused to start yesterday but today somehow it is working again and i am able to post this. Why is this happening to me?

i am using Intel(R) 82915G/GV/910GL Express Chipset which is 4 years old.

try disconnecting most of the hardware that u have connected to your pc and remove extra hard drives and dvd roms.....also try removing and reinserting the CMOS...if that doesnt fix it ,it wud probably mean that ur PSU is causing the problem