20' imac core duo.  I was reinstalling OS and files using Firewire and a 17" imac.  1/2 way through I aborted and it said "if you stop now you may not be able to restart your computer" I took no notice and pressed 'Stop".  Now every time I start the computer I get " you need to restart your computer......". I have tried booting from external DVD, another computer, reseting PRAM, SAFE start but no luck.  I do not know if it software or hardware problem.  I phoned Apple but they just went through what I had already tried so they advised me to take it to a Mac shop.  Trouble is nearest is 3 hours away.  When I start the message KP comes up after about 20 seconds but trying to boot from a USB drive you can see it accessing the DVD and it takes about 2 minutes for the KP to appear. Can anyone help? 

The 17" is an Intel and has an increasing level of vertical lines on the screen.  Also lately it has started freezing for no reason.  Have nothing attached but keyboard. So decided to buy a second hand 20" Core Duo( it's actually older than the 17").  I tried Migration Ass.  but for some reason it did not work with all files so I connected in Target mode.  I believe this is not the way to do it. I have a drive that I use for Time Machine but can't boot from that either. There is an OS.  X.4 stuck in the drive and won't come out.  The 17" is running X.6.8 and I believe the 20" was the same. Tried reseting PRAM

It's retail, but also have Leopard & Snow leopard.  Tried booting from all with external player. Ejecting DVD: Had Snow Leopard trapped inside, nothing would get it out until I poked around the DVD slot as I switched it on.  Out popped the DVD so though I would try a different OS version.  Tried mouse, eject but machine will let nothing happenS/N: W8604JT7U2P

It's retail, but also have Leopard & Snow leopard.  Tried booting from all with external player. 

Does the internal not work on the 20"? 

The 17 and 20 use the same RAM.  Maybe the RAM on the 20 needs to be reseated or maybe it's bad.  I'd try reseating the RAM and/or putting the 17 RAM into the 20.  Try booting from Leopard or Snow Leopard if the 10.4 installer DVD is earlier than 10.4.4, or it could be even if it is 10.4.4 on the retail they both came out the same month so maybe the 10.4.4 on the retail is not the right 10.4.4 to boot the 20.  Sometimes they slightly modify the same version of the installer to be specific to the particular model. 

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