Curious. I haven't seen a RH7.0 distro that installed itself automatically. Even if you selected the default "workstation" setting, it still should have asked you several questions, such as root passwords, and (relating to this) whether or not you want to use LILO, and then where to install it (MBR or not). Having said that:
1. Did you install RH after WinME? If you installed WinME second, it would overwrite your MBR, erasing any reference to RH7.
2. With a 20GB drive, did you split the drive down the middle, with 0-14.9GB for WinME and 15-20GB for RH? If you did and LILO is installed in the first bootable sectory (not MBR) of RH, then your system will probably never see it when it boots and you'll be stuck with a life of a boot-floppy.
3. Since you haven't invested much time in the OS yet, I would suggest reinstalling and going through step by step through a custom install. It's not much different that the default install, but you have more control over what's done with your system. And make sure that you put LILO in the MBR.
Even so, you'll have some problems with the way your drive is split right now. The latest versions of LILO should still be able to see your Linux partition, which is way past the old 1024 cylinder limit, but there are no guarantees. Do a search here on LILO and you'll find many threads on problems. I'm sure you'll find your solution there.