My G5 iSight iMac (20", 2.1GHz) has worked flawlessly since new, has been driven hard by youngsters playing games and with multimedia more or less 365 days a year, and has overall been a fine machine. It does not overheat, and it is virtually silent. It also looks fabulous.

Although I recently replaced it with an Intel iMac for much home use (e.g., to get NetFlix, which requires an Intel processor), we still keep the old gal alongside the new, and it frequently gets used by preference by all of us for many of the more usual things.

I'd hazard that the machine pictured is worth fixing if it has lasted this long. They were not all duds. So stick it on a shelf and wait for some replacement parts to walk through the door. With any luck you can find a whole dead unit and then do the required surgery.