If you don't tell us exactly what you have tried (with specific error messages and relevant output that may help to diagnose the problem) it is rather difficult to offer any specific advice. AFAICT, according to the ATI knowledgebase, integrated cards like the one you have are supported on the AMD64 architecture and should work. If you are really totally new to Linux, I would strongly advise you to read the stickies in
Linux - Newbie. And for a good introduction to Linux, I can recommend reading
rute (100% free e-book!) and also have a look at
the linux documentation project. I hope that helps, and best of luck with it!
P.S.
It just occurred to me that RHEL is a commercial product with installation/configuration support, so if you paid for the support why not use it? Just my 2 cents.
