In RH 9 there is an option to set program that startup when X starts. Go to the "hat" then Preferences, More Preferences, then sessions. There is a tab that says "startup programs" Put your program in there. The number associated with it is the "importance" of the startup program (sorry for the crappy word to describe). I would say set it somewhere between 80-100, but adjust according to your preference. This will also start everytime you log in to the machine, so not just when the computer starts. If you want it to start when the computer starts up ONLY, you could put the command into /etc/rc.d/rc.local.
Hope this was a help