It's been a long time since I did this, but what it involves is using the loadlin.exe program in the DOS batch file.
I think you copy your linux kernel to the DOS partition. It is usually symlinked to /boot/vmlinuz, so just copy this file there. It may be different on RedHat. You also need to know the devicename of your root partition.
In DOS, you just run loadlin.exe, and give it the kernel filename, and device name of the root partition in UNIX format of course.
Better yet, don't follow my sketchy instructions. Read the loadlin howto at:
http://www.linux.org/docs/ldp/howto/mini/Loadlin+Win95-98-ME.html