Yes! of course a power supply problem. Here's a step by step procedure in diagnosing this problem:
1. Turn on your computer. (ok I know it wont turn on but just turn the power on), check at the back of your cpu. is the power supply fan spinning? If not, then you'll have to throw away that power suppy & start buying a new one.
2. If the fan is spinning but the computer is still 'dead', open the cover & check whether all the power connectors is connected properly. Usually, they're 2 'female' power connectors that must have to be connected to the motherboard (1 is the biggest connector of your power supply & the other is a 2x2 hole connector (a square-shaped one). Try searching for a 'male' socket on your motherboard for these 'female' connectors. Maybe you forgot to connect one.
3. If the fan is spinning & you're extremely sure that you connected all connectors properly but the CPU still dead, Then check your RAM whether it is pushed/plugged properly onto the socket. You can try taking off the RAM from it & re-seat it again & then turn on your computer. Again, make sure it is properly pushed/plugged.
4. If still cannot, try you borrow a RAM from your friends (make sure you borrow a correct type of RAM and it's working well. Then fit the RAM onto your motherboard & try turn on again.
5. If still cannot on, ermm.. I don't know what's next. Maybe your processor???
I hope this procedure works but also, I do hope for other's opinions. Thanx!