Intel Imac 1.8G Duel Boot wont load OS

[Daveeringa]

Hi! My early 2006 17inch Imac has died! I was surfing the internet a couple of weeks ago, went to bed & when I came down in the morning the screen was off, but the computer was still on - the mouse was recieving USB as the light was on. I unplugged the power & restarted, but still the same problem, no screen & you could hear that the computer itself was on. I ordered a mini DVI to VGA adapter to connect the Imac to an old VGA monitor I have & that came this morning. I connected the monitor & started the computer and was horrified to read the massage "No bootable device -- insert boot disk & press any key". My computer is a duel boot, normally when you start it you are presented with 2 icons to choose from Mac or Windows, but now it appears to have forgotten that it has either OS!! I have tried to load it as a target drive via firewire to an old G4 laptop that I have, but sadly to no avail! HELP!!!!