Q--"Am a newbie in Linux, i want to create a bootable DVD which contains both Microsoft 2003 (2 cd's) and RHEL5 (one dvd)."
If you mean the "installer CD contents" from two separate system cd's into one DVD, yes you can contain the contents into one DVD. Most linux installers are below 700mb. You can make the DVD bootable under linux. But as to the Microsoft I have not heard it to run on CDs or DVDs yet.
You can use "mkisofs" command or "dd" in the terminal. Learn how to use it, type:
$ man mkisofs
$ man dd
also read some tutorials here:
Hope this helps.