Unfortunately, preparing for Red Hat Linux installation is a task with a number of potential pitfalls, which I try to flag on these pages. Note, however, that I'm not an official authority on the subject; I've no connection to Red Hat except as an occasional customer, and I haven't even studied the source for the installation programs. What I relate is based on trial-and-error, newsgroup postings, and my own (possibly flawed) reasoning processes. Take it for what it's worth, then.
I'm not going to cover Linux installation per se, or even creating a physical floppy disk from the various .img files. These topics are covered in plenty of other places. If you're a Linux newbie, I suggest you get a good book or start browsing at http://www.linux.org, which has lots of useful information and links to yet more useful information.
You have two basic choices when you download the files to burn a Linux CD: You can download the files individually and create a CD using the CD-R procedures with which you're probably already familiar; or you can download a CD image file (aka an "ISO image" or similar term) and burn that to CD. If you're planning to install from a local hard disk, only the first option will work.
In general, burning a Red Hat CD from an image file is easier and more likely to succeed than downloading the individual files and creating a fresh CD from them, but only if you've got a reliable enough Internet connection to get an entire ~500-650MB file in one go (or with an ftp program that can resume an interrupted download). Here are some sites that are reported to have Red Hat image files. I've not checked these to be sure they work, however.
You should keep some points in mind if you choose to download an image file:
Once you've obtained an image file, you'll need to burn it to a CD-R to use it. You do this in the same way you'd burn an image file you create locally with mkisofs or some other utility, using an option in your CD-R software to create a CD from an image file. Precisely what this option is called and precisely how you use it vary from program to program, so I can't provide detailed instructions.
If you want to create a CD with specific add-ons, or if you want to install from hard disk, you need to download the files. Use your existing machine to log onto Red Hat's ftp server (ftp.redhat.com/pub/redhat/redhat-6.0/i386), the Sunsite ftp server (sunsite.unc.edu/pub/Linux/distributions/redhat/redhat-6.0/i386), or some other location with the Red Hat installation tree (Red Hat maintains a list of mirror sites at http://www.redhat.com/mirrors.html. Locate the installation tree for Red Hat 6.0 (or a 5.x release, if that's what you want). You're interested in the following directories:
RedHat/
RPMS/
instimage/
lib/
modules/
usr/
bin/
etc/
base/
The RedHat/instimage/usr/etc directory is new for Red Hat 5.2, and the RedHat/instimage/modules directory is new for Red Hat 6.0. I don't know if either of these is strictly necessary, but they each contain few files, so there's little point in omitting them.
(Although I've provided URLs to get to these ftp sites from your web browser, that's a poor way to get a Linux distribution, since most web browsers only let you download files one at a time, and the Red Hat distribution contains far too many files to do this comfortably.) This directory tree likely falls under a "/pub/redhat/redhat-6.0/i386" directory, or something similar; the exact location will vary from site to site.
You'll also need either my joliet.img file (for installing Red Hat 5.0 from a Joliet CD or FAT-32 partition) or the boot.img file that should reside somewhere on the same ftp site as the rest of the Red Hat system. For hard disk installations, you'll also need the supp.img file. You'll need the RAWRITE.EXE utility (for DOS or Win95), LOADDSKF.EXE (for OS/2; it's on the OS/2 install CD), or Unix/Linux dd to create floppies from these .img files.
Ultimately, you'll want these to appear on your burned CD exactly as above. That is, under Win95 or DOS, if your CD is "D:", you'd want D:\RedHat, D:\RedHat\RPMS, D:\RedHat\instimage, etc. If you're installing from a disk partition, the directory tree must be as above, but can reside in its own subdirectory (e.g., C:\RH51\RedHat, etc.). Those installing from a disk partition may also omit the entire instimage directory tree.
I'm told that one useful tool for Win95 users is CuteFTP, available from http://www.cuteftp.com. I've never actually used this program, but I'm told it will download an entire directory tree with case intact. CuteFTP can be configured to download symbolic links as the files to which they point. Under the "Commands" menu, there should be an option called "get link as file;" select that option and you should be set. The popular freeware wu-ftp may or may not be able to get links as files; some people have reported success with this, but others (myself included) have failed. Perhaps wu-ftp has a similar option, or perhaps some versions are buggy with respect to symbolic links. (Symbolic links are important because they are used in certain directories in the Red Hat distribution; more details later.) I've also heard that the Windows program Bullet Proof FTP is good for this task, too, as it has a "resume failed download" feature that can help on flakey ftp links. I've never tried it, though.
Pitfall #1: Downloading the wrong directory tree. Red Hat assumes that its files will be laid out precisely as I've specified. As far as I know, there's no way to override this, so if you burn a CD incorrectly (say, by making the RPMS directory at the base of the directory tree for that CD), you'll have created a "coaster." FAT-32 installers have a bit more flexibility in this respect; you can put the RedHat tree inside another directory, but you do still need to have RedHat/RPMS and RedHat/base directories.
On my system, the main necessary files consume about 500MB (including duplicate files for links). That leaves about 150MB on a CD-ROM disc for supplementary material, like updated RPMs, part of the Red Hat "contrib" directory, StarOffice, updated Ghostscript RPMs, etc. Feel free to include them. It might also be a good idea to include both the original boot.img and supp.img files, and my modified joliet.img file (if you're using Red Hat 5.0). To do anything with these files on a system that doesn't yet have Linux installed, you'll need the DOS utility RAWRITE.EXE, which should be somewhere obvious on the ftp site from which you get the main Red Hat distribution. The DOS utility FIPS can also be handy (note that there's a version of FIPS available from http://bmrc.berkeley.edu/people/chaffee/ that supports FAT-32, and this version is now also in the Red Hat 5.1, 5.2, and 6.0 trees on many ftp sites). Put these wherever you want; it shouldn't really matter.
Some people have asked about creating a Red Hat CD which will directly install the updated RPMs from the updates directory, rather than the outdated RPMs in the RedHat/RPMS directory. This is possible, but tedious. I have short directions available here, but I've not tried this myself, and so can't guarantee the veracity of this information. I would advise Linux newbies to not attempt such a task; stick with installing a "stock" Red Hat system, and manually update the necessary packages as needed. Note that simply replacing old packages with new ones will not work, since filenames and dependencies must match or the installation will fail.
Pitfall #2: Case matters! Red Hat is fussy about case of files and directories when installing from CD, or from FAT in Red Hat 5.2. If you create the directory \RedHat\rpms or \redhat\RPMS or any other variant, it just won't do. You must get the case right or you'll be out of luck. This is true all through the directory tree! So check all the files, or at least all you can stomach. Compare against the directory listing from the ftp site. The best way to check filename case in Windows is to use a DOS command prompt. This will list the DOS 8.3 filename on the left and the long filename on the right. The long filename will be what will be burned to CD (usually; see CD Pitfall #3 in the CD section). The filenames shown in the Windows GUI may be changed in various ways (which are configurable in Windows 98). Also, keep this in mind if you burn a CD, since CD-R programs might decide to change things. Note that there's an extra case-related complication for Red Hat 5.2 FAT installers; see the FAT-32 section for details. If you download your files in Linux but need to burn from Windows, be aware of the fact that Linux and Windows treat case differently on FAT partitions, so you may need to adjust some files' case after you've downloaded them.
Pitfall #3: Exact filenames matter! This is true even of the contents of the RPMS directory. Some networking software for Windows may try to change filenames, so keep an eye out for that. One or two missed RPMs may not be a big deal if they're non-critical, since you can install them manually later, even if they're recorded with the wrong filename; but you don't want to be doing this for dozens of packages. This is doubly important for the contents of the \RedHat\instimage directory tree, since these are programs and libraries that the install routine will be running during installation. Note also that MacOS's HFS may not be adequate to maintain the complete filenames of all files, so Mac users who have Joliet creation capabilities may have to check for incomplete filenames at burn time.
Note #1: Red Hats 5.0 and 5.1. Pitfalls #2 and #2 don't apply or are irrelevant to installing Red Hats 5.0 or 5.1 from FAT, though they're still relevant to CD installs of these versions. FAT installers of Red Hat 5.2 must still pay attention to these issues, though, as detailed in the FAT-32 section.
Now is a good time to read the CD-ROM or FAT-32 sections, to find out what pitfalls lurk with those installation methods.
There are also a number of Red Hat 5.0-specific pitfalls and comments of which you should be aware if you're trying to install Red Hat 5.0. These don't apply to the more recent 5.1 and 5.2 distributions, though.
The Mandrake Linux distribution is a variant of Red Hat Linux. Mandrake 5.x included the KDE GUI environment, which Red Hat did not at that time. Red Hat 6.0 includes both KDE and GNOME, so I don't know what Mandrake plans for their 6.0 release. I've never used Mandrake, but I'm told that the instructions I've provided here apply equally to Mandrake. You can also obtain Mandrake CD images from a number of sites. Try http://www.linux-mandrake.com/en/ftp.html for a list of Mandrake mirror sites, many of which have CD image files.
You should now be able to install Linux. With any luck, you won't run into any further problems. I've done a couple of test installations with this modified Red Hat 5.0 boot floppy, and the procedure seems to work fine. I've also installed Red Hat 5.1 from both FAT-32 partitions and from a Joliet CD, and it works fine with the original Red Hat 5.1 install floppy, with the caveats on the FAT-32 and CD-ROM pages. Similarly, Red Hat 5.2 installs fine, with the same caveats, plus more for FAT-32 installs that are detailed on the FAT-32 page. Red Hat 6.0 installs fine from Joliet CDs, as well.