Adding a Case-Fan to my machine

[Parpic]

I have a few spare fans pilfered from retired machines. They are 3-pin, 12v fans.

When I plug them in and boot the machine, they don't go.

I've looked through BIOS thoroughly, and don't see any kind of sysfan or setting which would otherwise help.

How can I make these fans spin? And thank you, in advance...

 

[Parpic]

Update:

I tested the voltage on the motherboard, and the pins are live, but underpowered. When I plug the fans into a test machine, they both still work. The pins get a much higher reading on the voltmeter on the test machine than on my main machine, (on which they don't work). My main isn't great (foxconn on a Dell GX620), and it's the next thing I intend to upgrade, but the machine is otherwise pretty good.

I run a 650w PSU... what can I do to increase juice to the 3-pin?

It just gets me that I can't plug in a case fan to this cruddy, but otherwise trusty mobo!

Thanks for the help...