I happen to have created a Virtual Machine (on VMWare Server) with Oracle Enterprise Linux 5.0. This one I had available at the moment, I did not have a clean VM with RedHat Enterprise Linux 4.0.
The problem you'll encounter then is that according to the Oracle Universal Installer the database is not certified on Oracle Enterprise Linux.
You can solve this by starting the installer with:
1 2 | . /runInstaller -ignoreSysPrereqs |
Happy installing.