1. I strongly suggest you clean the dust off your motherboard and other internal components, it is possible that may be culprit if nothing was changed since the last time you used.
2. if something was in fact changed and cleanning does not resolve issue try the following to recover the hardware default status, and then making the motherboard work again:
Step 1. Switch off the power supply unit and then switch it on again after one minute. If there is no power switch on the power supply unit, disconnect its power cord for one minute and then reconnect.
Press and hold the <Insert> key on the keyboard, and press the power-on button to boot up system. If it works, release the <Insert> key and hit <Del> key to enter the BIOS setup page to apply the correct settings. (load default settings and save changes and exit)
If the situation remains the same, repeat the procedures in Step 1 for three times, or try Step 2.
Step 2. Switch off the power supply unit or disconnect the power cord. Open the chassis cover. Locate the CCMOS jumper near the button battery. Change the jumper position from default 1-2 to 2-3 for one minute to discharge the CMOS data, and then put it back to default 1-2 position.
Close the chassis and switch on the power supply unit or plug in the power cord. Press the power-on button to boot up system. If it works, hit <Del> key to enter the BIOS setup page to do the correct settings.
If the situation remains the same, try Step 3.
Step 3. The same procedure as Step 2, but while discharging the CMOS data, pull out the ATX power connectors from motherboard and remove the button battery during CMOS discharge.
3. try replacing the powersupply