According to millward:

In grub.conf I added hdc=ide-scsi and Red Hat automatically updated fstab during boot. cdrecord -scanbus showed a device at 0,0,0 I had prepared a file in /usr/LTSP using mkisofs -r -J -o /usr/LTSP/ltsp.iso /usr/LTSP ( got this from an English Linux magazine. I can never understand man documents ) So I tried to burn a CD using cdrecord -v dev=0,0,0 speed=4 /usr/LTSP/ltsp.iso and it looked good. I booted into ms windows and the CD is readable under DOS too. Thanks for all the advice. I would never have figured this out on my own. Strange that in 7.2, grub didn't need the statement hdc=ide-scsi, but I quess things change all the time. Thanks again!

Actually, grub itself doesn't need any of that, it simply passes it on to the Linux kernel. :) But the kernel would have needed that all along.

I suspect it was getting it from someplace else before your 7.3 upgrade. Since you seemed to have an appropriate append statement in /etc/lilo.conf, I suspect you had been using LILO previously, and just switched to grub in this latest upgrade. Since grub is the default selection, it's easy to do that without even realising it.