Here, I found this for you:
https://help.ubuntu.com/community/Oracle10g
I hope you find it useful.
EDIT: Alternately, if you cannot get it to work and want to move on to RHEL, why specifically RHEL? I highly doubt anyone would just have an ISO of it laying around, simply as it's not a monetarily-free Linux distribution. Why not use Fedora or CentOS?