Don't plug in power from the wall directly to the board!
The "power supply" also converts the 115 AC to considerably lower DC power.
Did you look on the back of the power supply? Sometimes they have a toggle thumb switch to turn it on.
How old is the computer?
I wouldn't buy a new MB for the computer unless it's new enough to warrant it because you'll have to make sure the new MB is compatible with the RAM and the CPU, etc.
MBs can be had for reasonable prices and you could build a decent computer (meaning just the tower with recommended new HD) for your mom for less than $250 and use the monitor, mouse, and keyboard she already has.
The "power supply" also converts the 115 AC to considerably lower DC power.
Did you look on the back of the power supply? Sometimes they have a toggle thumb switch to turn it on.
How old is the computer?
I wouldn't buy a new MB for the computer unless it's new enough to warrant it because you'll have to make sure the new MB is compatible with the RAM and the CPU, etc.
MBs can be had for reasonable prices and you could build a decent computer (meaning just the tower with recommended new HD) for your mom for less than $250 and use the monitor, mouse, and keyboard she already has.