Jeff Wiseman wrote:

You might want to make sure that there isn't a shutdown script in your startup folder (a popular joke around some offices). If you have the original CDROM that came with the iMac, try booting from it. If it lets you boot and run, then go check out the startup folder on your hard drive. Otherwise, if it still shuts down then you have a hardware issue. Also, try starting it up with the keyboard disconnected--a faulty powerswitch on the keyboard might create such a problem as well.

BTW, if you don't have the original CDROM (or any other that you can boot the iMac from) I believe that there is also a way to do a minimal power-up by holding down certain keys during powerup but I can't remember the sequence.


I know it's a hardware problem. It never gets far enough to detect the
hard drive, or even have the monitor warm up. I suspect that the
monitor/power supply is at fault.
--
Andy Cuffe