I got a 741 and a few resistor.
I have +3V, +12V and ground legs from the PC mother board.
Now I want to create an output of +9V with the 741.
Would you please help me with this circuit???
Thanks a lot!!!!

 

Easy. Lose the 741 and measure the voltage across the +12 and the +3. Should be 9V. Done.

But to get serious, you need to provide more information about what you would like to do; how much current, are we talking DC? An op-amp doesn't create power - it just amplifies tiny signals to larger - but still small - signals.

 

Well...yes, we are talking about DC.
I made a breathing (fading) LED circuit for my PC power LED indicator.
But it requires 9V to supply for that circuit (555 IC, 2 capacitor, LED....).
So the +3V of the power LED leg on the mother board is not enough.
Though, the mother board consists of a few +12V leg for cooling fan.
So on the motherboard, i got +3V, +12V, (+5V : USB also) and ground.
I need to create an +9V leg to supply the breathing LED circuit.
So please help me with the most simple solution.

 

Post the schematic and we'll tell you which resistors to change...if any.