My parents in law have an iMac model 2105 (20 inch, Core Duo 2GHz, 250GB), which I am having a look at. I have managed to start it once (!) and checked the harddrive using Disk Utility - no problems reported. Upgraded to latest 10.6.8 without issue, powered down and could not power it up again. Now the machine is in fine shape otherwise; no abuse, no smoking, no nothing. I am taking it apart, but so far it has not revealed anything; usually when pressing the power button, nothing happens: no sounds, no lights, no fans spinning (I can see the exhaust fan not spinning). My father in law reports that it does indeed start from time to time. Any input on what could be wrong or what I might want to test, are most welcome. Maybe the machine is just old and should be replaced, even if it works just fine when running?