Red Hat 9 doesen't resolve dependencies with its package installer (Add/Remove Applications) or when installing rpms. This can be a headache especially for users new to GNU/Linux - luckily, there is a simple command line program - apt for rpms - which is good at resolving library dependencies. I recommend this as a great easy install tool for Red Hat.
Follow the instructions in the above hyperlink (e.g. download apt rpms, "rpm -Uvh apt*", configure http repositories & "apt-cdrom add" [both optional], "apt-get update", "apt-get install gcc").
Note that when using and installing apt-get you need root permissions - remember "su" and "su -" give you temporary root privileges (or privileges and root path, respectively).
You will definitely need 'gcc' and possibly 'make' as well. You can also use apt-get for installing and updating a lot of major applications such as mozilla (apt-get install mozilla).
I'd like to point out that Fedora (successor to Red Hat 9) includes apt for rpms by default in its distribution: