For both the installation and the post-install configuration, it's important that you have a complete and accurate list of your system hardware setup, such as network card, video card, monitor make and model and so on.
You should also have verified that all of your hardware is compatible with Red Hat Linux, which keeps a current list of supported hardware at http://hardware.redhat.com/hcl/.
It's critical to truly understand the hardware you have on your system. Case in point: many new systems, particularly laptops, come with what is claimed to be a built-in "modem". Invariably, these are not fully-functional modems, but are rather what are referred to as "Winmodems"; that is, much of their basic modem functionality has been transferred from the modem into the Windows operating system.
If you don't understand this distinction, you will almost certainly go insane trying to get them to work under Linux without installing and configuring new software (covered in a later chapter). Your safest strategy is to accept that, if you have one of these Winmodems, then you just don't have a modem. Period.