I just spotted this, hence the late solution. Perhaps this will help someone in the future.
Yes it is possible.
Observe the color code of the insulation of the wires.
1) Orange wires are 3.3 Volts
2) Red wires are 5 Volts
3) Yellow wires are 12 Volts
4) The Green wire is the Soft Power On wire
5) All Black wires are Ground wires. Doesn't matter which Black wire it is, it's a Ground wire.
(It isn't a Common wire. This is DC electricity, not AC)
These are your main voltages, and wires to be concerned with.
Fortunately all HP, (Or any proprietary computer manufacturer in that time period), did, was to change where the wires are placed in the 20, or 24-pin ATX main power cable connector.
They just moved the wires in the socket holes, didn't change the color code.
1) To remove the wires in the ATX power supply, main power cable connector
2) To remove the wires in the proprietary computer's ATX main power cable connector.
BE SURE to make a concise, clear, drawing FIRST, of where the colors of the wires went in the proprietary connector, BEFORE you remove them!)
3) To reinstall the wires into the proprietary connector.
(Again. Following the color code of the wires you removed)
Removing the wires out of the 20, or 24-pin ATX main power cable connector:
Observe these photos, of a 20-pin ATX main power cable's connector. This procedure can be applied to a 24-pin ATX main power cable connector also. (Or a 20 + 4-pin ATX main power cable connector)http://www.playtool.com/pages/psuconnectors/connectors.html#atxmain20
(Also gives you information about the color code of the wires)
The middle photo shows you a view of the Front of the connector.
The photo to the right shows you the Back of the connector.
Where the wires go down into the connector is a Socket Hole.
At the end of each wire is a metal pin connector. A Male pin connector.
This metal pin connector is shaped like a tube on the end, and comes up to a square shape as you go up.
The square shape fits the square socket hole.
On one side of the square shape is a Tang. It's part of the square metal shape, and sticks out away from the square shape.
Resembles a barb on a fish hook.
In this crude illustration, let a small L represent the side of the square shape, and this forward slash - / represent the tang.
This is an illustration from a manufacturer that supplies this type of metal Male pin connector,http://www.molex.com/molex/products/datasheet.jsp?part=active/0002092166_CRIMP_TERMINALS.xml&channel=Products&Lang=en-US
A needle with the proper thickness so it won't bend, is inserted into the Front side of the socket hole, and is used to depress the Tang.
If you look down into the back of the connector, and into an individual socket hole with a bright light, and a magnifying glass, you will observe that the square socket hole has a small notch in one side.
This is where the tang slides down into.
It isn't easy to see from the front side.
The tang is depressed using the needle from the FRONT of the ATX main power cable connector, and the wire is removed from the Back side of the connector.
The metal pin connector's tube shape only goes up so far, then it turns into a square shape.
The socket hole in the connector is shaped to match. Tube shaped hole at the front of the connector, square shape coming on up to the back of the connector.
The square shape's corners, of the metal pin connector, keep it from coming out of the Front of the ATX main power cable connector.
The tang keeps the metal pin connector from coming out of the Back.
More information about the color code of the wires in an ATX main power cable connector, (Scroll towards the bottom of the page)http://en.wikipedia.org/wiki/Computer_power_supply