Swap a PII power supply with a P4?

G’day

I have an old HP with an Asus KL97-XV mobo which i’m led to believe is made especially for HP.

The Power Supply is dead and a lovely man from the HP Trade Center said he will kindly send me another one for the same price that I paid for the half decent full tower P4 case with 400W P/S.

The dead power supply had a 3 female pin connector (P8) to the mobo marked PS FAN and from the mobo doco is two ground pins and a +12V pin in the middle.

Is there some type of connector changer or something that will allow me to use the 400w P4 power supply???? When I boot disconnected, I get HDD, case fan, and Floppy action but no video and no further.

Any thoughts are appreciated.