Once, i loaded the the default settings in my bios menu and after that my pc went off and when i tried to turn it on, it just showed the light and went off.. its happenning repeatedly... what do i do ? can any1 tell me what could be the problem? Moreover i overclocked my graphics card before setting the bios into default mode... Help would be appreciated...

I'm no expert. But it could be that a certain default setting in bios doesn't agree with your overclocked graphics card.
Try resetting your graphics card to factory default as well.
If possible.

well, graphics card automatically gets default at the startup.... my cpu speed is 2.93ghz.. bt the bios was showing that its operating on 1.60 ghz.

Can you boot into the BIOS? If not, then your hardware is starting to fail. If so, then reset to factory defaults and see if it boots. If not, then the hardware is starting to fail...

try to reset your cmos, unplug your computer and hold down the power button for 30 s, try to boot, or take out the cmos battery for awhile

reset your bios into factory defect....

Try:
- Check your memory card and graphics card, whether they arre well seated.
- Check the Power supply unit(PSU).verify whether the fan is running.
- Replace the 3v motherboard battery.

SNIP