It was the graphics card.
I fitted the ATI Radeon HD 5770 1024 MB as several sources say it works with the Mac Pro 1,1 and it does.
My system booted fine to an install DVD, then I put the boot disk back in...
I've decided that it must be a Graphics card issue, so I've ordered a replacement.
Will report back.
Weird issue, but as you say sound is okay, USB keyboard and mouse all work fine, a mouse cursor on the screen is...
I've tried everything, short of lugging it to an Apple Shop.
it won't get to the login screen.
The boot disk is fine - I connected to it via target mode and 'repaired' it.
I've fsck'd it, reset PRAM and...