Okay, easy to do with one hard drive. The absolute easiest way is to use Win98 fdisk to make two partitions. Load Win98 on the first partition. Load Red Hat on the second. Put the Grub or LILO boot loader in the MBR and it should work fine.
For the detailed instructions, go to the source:
If you haven't registered with them, you might be asked to do that first--no cost, just give them a user name and password. When you get the list of manuals, you want the 8.0 section, "x86 Installation Guide"
There are three flavors--pick your poison and go to Appendix G (page 121) and follow the yellow brick road!