Then it's your power supply problem. It only have enough power to light up LED but not the motherboard itself. Consider buying new power supply for your desktop or if you have old computer or other computer that you use, try to salvage it for a while and try it on the faulty computer. If it's on, then most likely your power supply is dead.
Mudi- commented: Solved my problem! :) +1
Dcurvez commented: this is a mystery to us all- good suggestion! +3
wenbnet commented: Thank you dear... +0
wenbnet commented: You Can. Wih Good title. +0
wenbnet commented: Good suggection. +0
MoZo1 commented: AHCI lol, you noticed it! +3
jingda commented: Same thinking as me above about the shouting part +10
jingda commented: Exactly what i said above:) +10
Anuradha Mandal commented: Right +0
jingda commented: Yo, buddy +9
jingda commented: Excellent. +9
jingda commented: Glad your Avast problem is solve. Way to go, Flagstar +9