Welcome to the forums!
Let me give you some valuable beginner advice: Red Hat 8.0 is obsolete and unsupported
. Ubuntu 8.10 is obsolete and unsupported
. Don't use them!
Download a currently-supported distribution and you will have a much more pleasant introduction to Linux. You can read more about the different distros and what is the latest release at http://distrowatch.com
(I personally use and recommend Debian, but Ubuntu and Mint are also very popular choices for beginners.)
Here is an easy how-to so you can start using Ubuntu (current release, please!) with no permanent changes or risk
to your currently installed system/data: http://www.psychocats.net/ubuntu/virtualbox
(While the guide is written for Ubuntu, you can also use the same concept with other distributions.)