You can either try to boot your existing system (and then reinstall grub), or you can use some sort of repair system to reinstall grub first. I assume since you're asking this that you don't have a boot floppy.
A Knoppix CD is your best option. You can either use it to boot your existing system, or just boot Knoppix, reinstall grub, reboot, and things should be okay.
If you don't have Knoppix, various install disks will let you boot to an existing partition if you know its name and number. If they give you a boot prompt, append "root=/dev/hda2", or whatever partition your install is on if not hda2, to the kernel's arguments and that might get you in.
You can try some RH9 boot/install floppy for the above, or your RH9 install CDs, or a Slackware repair kit. With the latter two you'll also be able to get to a shell prompt (the RH9 CD should offer you some sort of help about this when you boot it up), chroot into your existing installation, and run grub-install from there. You can get the slack repair disks at <
ftp://ftp.cerias.purdue.edu/pub/os/s...lackware-10.0/>. Pick up an appropriate bootdisk from the bootdisks directory, and then the rescue.dsk from the rootdisks directory.
If you have a nonstandard system (unusual hardware, ReiserFS root partition, etc.) you'll need Knoppix. It's always a good idea to have a Knoppix CD around anyway (just as it's a good idea to make a boot floppy when the installer suggests that you make one
).
It's not a huge problem, just potentially tedious. Good luck.
