G4 DP 1Ghz 4Gb-ram 750Gb storage.
I had an interrupted update. Now it will not start.(grey screen to shut off).
I can not reinstall OS 10.4, The tray is open and will not stay closed.
Any hints would be appreciated.

A PRAM reset will likely take care of the tray staying open.
You could take some of that RAM out. No G4 supports that much RAM, with a maximum of 2GB on some G4s, others hold less than that.
Perhaps you don't have a G4, but do have a G5?

I will try the PRAM reset.
And Your right four sticks of 512.