anybody knows how i can open the cd tray from the powermac g5 if my hard drive wont start up and i have to use the installer cd operating system??

hold down the mouse button and start the machine. keep holding it down until it ejects.

or . hold down apple+option+O+F and start. at the prompt , type "eject cd"

With the mac shut down, you can also open the tray by opening by hand the alu door then insert a trombone clip in the tiny hole there should be somewhere (on mine it's 1/3 left in the lower visible part of the burner).

Now, it should push the tray enough to be grabbable with one hand.

Never force!
The clip should ask a bit of pulling but it should go "smoothly"

You can shut the tray by just pushing it back in place.

You can also use the eject key on the keyboard if you start up into the Startup Manager (hold down the option key during boot until you have a blue screen and a couple of arrow keys). At that point, the eject key will open the tray and allow you to put in your disc. Then click on the circular arrow (refresh) to have the G5 scan your bus again. Once it finds the CD/DVD hit the right arrow button and your G5 will boot from your optical drive. There is also a way by booting into single user mode, but it is a bit more complicated.

peace