Well here is a way to check your power supply, on your hard drive connector using your volt meter and measuring from ground. this would be using one of two middle connectors it should measure +5 VDC on the red wire and + 12 VDC on the yellow wire. If these voltages are good then we got to see if the power supply is producing the -12VDC voltage. This voltage is ussed by the syustemboard on pin 14 of a 24 pin power supply. I would recommend not having your system board plugged in while measuring these votlages, but the power supply may need a load, I would plug in the cdrom.. Below are a couple of picture to explain this and a link to a website that has this documented.
http://www.playtool.com/pages/psuconnectors/connectors.html
The 24 pin main power connector was added in ATX12V 2.0 to provide extra power needed by PCI Express slots. The older
20 pin main power cable only has one 12 volt line. The new 24 pin connector added one line apiece for ground, 3.3, 5, and 12 volts. The extra pins made the
auxiliary power cable unnecessary so most ATX12V 2.x power supplies don't have them. The 24 pin connector is polarized so it can only be plugged in pointing in the correct direction.
Pinout
Pins 1 through 12
Pins 13 through 24
Description
Wire color
Pin number
Pin number
Wire color
Description
+3.3 volts
orange
1
13
orange
+3.3 volts
+3.3 volts
orange
2
14
blue
-12 volts
ground
black
3
15
black
ground
+5 volts
red
4
16
green
PS_ON#
ground
black
5
17
black
ground
+5 volts
red
6
18
black
ground
ground
black
7
19
black
ground
PWR_OK
gray
8
20
white
-5 volts (optional)
VSB +5 volts
purple
9
21
red
+5 volts
+12 volts
yellow
10
22
red
+5 volts
+12 volts
yellow
11
23
red
+5 volts
+3.3 volts
orange
12
24
black
ground
Good Luck I hope this helps.