Flashing question mark
Hi,maybe some advice please.
I have an imac 20" G5 als.running 10.5.8 The problem is that when I startup it goes to the flashing questionmark mode.I will explain what i have done so far.When this first happened I thought that the drive was playing up,so I attempted to install the system disk OSX but it was having none of it.after trying lots of times it eventually loaded,and I went to disk utillity,but it never saw the hard drive,so I thought that it must be the drive.The diagnostic light inside on the logic board were lit up as they should be.I purchased a new drive,and a battery for the logic board just in case,I installed the battery,and the new drive and started up,but yet again it went to the flashing questionmark.I shut down and started into the startup manager screen where I got a blue screen with a refresh symbol on the left and an arrow on the right but nothing where the drive should be seen.I reset the pram,and tried to start in safe mode which all brought me back to the questionmark .As a last resort I then installed a drive I knew was working because I replaced it for a larger one,and the exact same thing is happening and the system disk refuses to load.Can anyone tell me if I am doing things in the correct order,or I have missed something simple that I could try.I have installed a drives before with no recognition problems.If i get any answers I would be happy.Thanks
iMac, Mac OS X (10.5.8)