Help! Dead iMac but no reason. Flashing ? mark

I recently sold my iMac G4 on ebay. To clear information, I performed clean install and then installed OSX 10.1 and upgraded to 10.2 from disks I had. When I mailed to buyer, he mentionned that it would not work and had flashing ? question mark on screen. He returned item to me. So I now have iMac with flashing question mark. I tried to install Mac OSX again but it can't find hard drive volume to install to.. I also have Mac OS9 disk that I could try install with I suppose. Does anyone have any idea what I might have done or what can be done to affix?

It sounds like maybe the Hard Drive failed. Maybe the shipping to the buyer jarred it enough to make it fail. Not sure. But if you try to reinstall and it can not find the Hard Drive, either the drive failed or maybe shipping the Mac made either of the cables to the Hard Drive come loose.

Can Disk Utility see it?

(Boot from the OS X CD, Utiltities menu and Disk Util')

Vicky