Is this PSU half-dead?

[mitk0o0o0]

I got my hands on an old rig today and for some reason it will not properly start up. All I know is that it has the following components:
240W PSU
Asus P5GD2-X motherboard
NVIDIA 6600 GT GPU
1x 256MB DDR2 RAM
SATA hard drive.

So when I power on the computer, the light on the motherboard switches on, and both the CPU and PSU fans begin to work. There is no beep and no light appears on the keyboard.
The monitor keeps switching from Digital to Analog until it eventually gives up.

Also I keep hearing this sound which I believe comes from the hard drive: http://vocaroo.com/i/s0GB3nLI1Ket
It's as if it goes into a power-on loop.

When the hard drive is taken off, I still get the same results except for the weird power-on sound loop.

Any ideas on what to try? I do have another PSU but unfortunately it's with a 20-pin while this mobo needs 24.

 

[wernstar]

Either PSU(3.3V and/or 5V) or Mainboard is dead. The sound you keep hearing is the harddrive spinning up.

 

[mitk0o0o0]

Either PSU(3.3V and/or 5V) or MainboaCrd is dead. The sound you keep hearing is the harddrive spinning up.

Could that also be the reason why the hard drive keeps spinning up infinitely?