how do I reset imac G5

What problem are you experiencing with your machine?

you need to reset the Mac's PRAM, NVRAM, and Open Firmware. Shut down the Mac, then power it up, and before the screen lights up, quickly hold down the Command, Option, P, and R keys, until the Mac has chimed twice more after the powerup chime.

Then, before the screen lights up, hold down Command-Option-O-F until the Open Firmware screen appears. Then enter these lines, pressing Return after each one:

reset-nvram

set-defaults

reset-all

"The reset-all command should restart your Mac. If so, you have successfully reset the Open Firmware settings."

http://support.apple.com/kb/TS1812?viewlocale=en_US

Should the fail...

Try taking the battery out for 10 minutes. Put battery back in. Cross fingers. Power the machine back on.

How to eject a cd from the internal cd drive:

eject cd

List of devices:

devalias

List of variables:

printenv

More than you ever wanted to know about open firmware

http://www.firmworks.com/QuickRef.html

( nvram is the equivalent Mac OS X terminal command. )

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Resetting your Mac's PRAM and NVRAM

http://support.apple.com/kb/HT1379

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reset the PMU

http://mrjcd.com/junk/PMU.jpg

http://support.apple.com/kb/ht1939