Hardware: Imac 20, 2 GHz PowerPc G5, 2 GB DDR SDRAM, internal hard drve MATSHITADVD-R UJ-845 Operating System: OS 10.4.11 Serial # W85200D2SDZ Yesterday I started the Imac and left the room while it was booting. When I returned a short time later, the only thing on the monitor was a screen full of background blue, a restart brought the system up normally. The computer operated normally for the next few hours, but after about 5-6 hours it stalled between images on the screen saver. Everything was dead, so I rebooted the system using the power button. With this reboot the system came up with the normal gray screen/apple logo and went to the spinning progress indicator after about 30 seconds, about 30 seconds after this the screen went to the same solid blue and proceeded no further. No mouse no keyboard, no nothing. I tried several restarts, unplugged the power cord and restarted to clear the PMU. No luck. After about the 4th restart I let the blue screen remain in place for more than a couple of minutes. After about 3-4 minutes there was a slight shift in the blue color, and the arrow cursor appeared and the mouse was able to position the cursor. Of course there was nothing to position it over. The computer will boot in Safe Mode, and Single User Mode, it will also boot from the Tiger installation disk. I booted in Single User Mode and ran Applejack in both the regular and deep cleaning modes. No dice. I also booted from the install disk and ran the Disk Utility which showed no errors, also corrected permissions from the Disk Utility. Ive restarted while holding down the p, r, option, command keys to clear PRAM and NVRAM. I tried to run the Apple Hardware Diagnostics from the Tiger boot disk, and the first 3 tests came up normal. It seemed to stall out on the memory test. Documentation said the diagnostics should run from 5-15 minutes depending on hardware config after 45 minutes, most of it during the memory testing, I gave up on it. Perhaps I lack patience. While in Safe Mode, the Imac seems to operate fairly well, although I miss some of the features that Sale Mode cancels out, and it takes for ever to boot up. The next step will to be to crack the case and reseat and rearrange the memory chips and check for bulging capacitors. Id appreciate any additional suggestions and ideas that anyone might offer, hardware or software to try. Thanks in advance for any help.