Hello there AngelicKnight!!!
Welcome to LinuxQuestions.org. Well, the iso you've downloaded for Redhat 9.0 has to boot. If it does not, maybe:
1 - check your bios to see if it's enabled to boot from the CD.
2 - you may have downloaded a broken iso. Perhaps you've to download again.
3 - you've burned it wrong. You've to mount an iso before burning the file to the CD. I'm writing a mini-how-to to burn an ISO image correctly
with Windows and Nero, hope it helps:
1 - Open Nero
2 - Don't be ashamed to ask help to the Wizard
. When Wizard mode appears, do: compile new CD >> other cd formats >> create a cd from image file >> finish.
3 - A window will pop-up asking you to locate your .iso image. Find it and double click on it.
4 - it's your call now... speed to burn, test or burn at once...
That would be a bootable CD (Redhat first disc/image).