Sorry, I was going by the image oldskool posted. I pulled it up on Newegg and see that it is a different board. The power goes on the 4th and 5th pins from the right on the bottom row (PWRSW in the diagram). Sometimes the front connectors are flat on one side so you know which direction it goes on, sometimes not. I haven't fooled with any Gateway mobo swaps so I don't know about them.
The main ones you need are the power and HD activity light (IDE_LED). If you have a reset switch (RESET) hook it up, same with a case speaker (SPEAKER).