Well, my problem is solved. It ended up being a corrupt hard drive. After swapping out RAM and hooking up an external hard drive, it started up normally, albeit without the chime. Disk Utility saw the internal drive, and when I tried to repair the hard drive, it came up with up severe "unrepairable" problems. I reformatted the drive and reinstalled Leopard and now the machine is up and running. I also zapped the PRAM and now the chime is back again. Glad it wasn't power supply, or worse, logic board. Thanks for the info.