If that were a grey screen with rotating line, I could say I've seen it trying to boot from an OS10.3 installer CD when the unit (old iMacs) didn't have enough RAM. Also when trying to boot old units from newer AppleCare diagnostics OS10.3 CD. So now my best guess would be do the try new RAM. OWC (eshop.macsales.com) often has good prices on good quality RAM for older units. HTH On Wed, 27 Aug 2008, Peter Nevett wrote: . . . > I took your advice and followed the steps outlined earlier: boot from > OS 9 cd, zero the hard drive, reformat, boot from OS X cd. > Then nothing! Just a blue screen with an endlessly rotating line. . . . > Any more suggestions? Maybe I need to replace the memory? . . .