Since you have updated your kernel, you will have to download the sources from the web. The kernel sources that are supplied on the CD are likely _not_ going to work for you. So, here's a link to the current redhat kernel sources: ftp://ftp.redhat.com/pub/redhat/linu...-13.9.i386.rpm
Fair warning, this is nearly 40MB in size in case you are working on dial-up.
If that site is busy, you can check for mirrored sites on http://www.redhat.com/mirrors.html
Once you have the file, just do an rpm -i kernel-source-2.4.20-13.9.i386.rpm and you "should" be good to go. Good luck