Is the motherboard from my Imac really fried?

Hi there....
I have an Imac DV400 (summer 2000 I think) that wont start al all.
When I turn it on I get just a green led and some Harddrive noises.

I tryed changing the battery and resseting the Logigboard but nothing happened.
I measures the voltage all over using the service manual and a multimeter, and this is what I got:

Battery: 3,61v OK
Trickle voltage at J9: 4,9v OK
CDO Voltage at C10 with computer OFF: -1,1v OK
CDO voltage with Computer ON: 24,8v insted of the 21v according to the manual.
Down-converter: Pin2: 11,9v OK
Pin 4: 4,9v OK
Pin 14: 3,3v OK
PAV-board, Fuse F901 is OK.

As you see the only "funny" measure was in the CDO voltage in the motherboard when the computer was on. I got 24,8v instead of the 21v listed in the service manual. Does this means that the motherboard should be replaced?

AHH I got this Imac as a present and I dont know if the previous owner tried to install osX. Could this lead to my problem ?

Any other sugestion would be appreciated!!!!

THANKS

Yes, I've done it...... thats what I meant with resseting the logic board