Thanks to the help of folks on this forum, I now have my Centos 4 box up and working, however I do have a question on how the repair actually worked.
After starting the Linux Repair, the process "found my installed Linux". Some of you will remember that I had accidentally erased the /boot and /boot/grub directories, but I had most of the files saved (not the symbolic links) and put them back into the directories *and* I did run a rpm reinstall.
When Linux Repair "found the installed Linux", did it create a new /boot and /boot/grub *or* did it just use what I had put there?
When booting into "rescue" mode with the RH/CentOS installer disk, it searches for filesystems that look like a Linux installation and mounts them so you can fix them. The rescue system doesn NOT change anything - that was you who did it by running grub-install or whatever. So, I think nothing has changed in your /boot directory despite the things grub-install may have touched.
Simon