I have an iMac G5 (the one with the iSight). When I switch it on, the white power light on the bezel comes on but that's it. Is there any way of running a diagnostics check on it? The hard drive was recently replaced and I'm wondering this: what would the symptoms be of a failed HDD? On Windows I know it will say something like Invalid System Disk or No Disk Found. What would the iMac do? Would the LCD still power up even if the drive was faulty?