Power supply pin out

Can anyone tell me how to get the pin out (signal/power on each connector pin) information for the power supply in my PC. I have a Dimension 4300 with power supply model HP-P2507F3P.

 

The solution guide says to "check the power properties" and to use the "Tell me How" help file on the computer. This seems kind of a silly direction since the computer won't power up??

 

Thanks.