This article is from the CD-Recordable FAQ, by Andy McFadden (firstname.lastname@example.org) with numerous contributions by others.
You don't. The CD-ROM doesn't actually have that much data on it.
Some CD publishers use a trick where they reference the same spot on the
disc several times with overlapping files. This is common on software
installation discs with support for multiple languages. A separate
install directory, with a full set of files, is created for each language.
Any common files, such as installation routines or language-independent
code, are written to the disc once and shared by all. If there are ten
directories, and each points to a 50K shared file, it will appear that 500K
is in use. If you try to do a file-by-file copy from the disc onto your
hard drive, you'll end up with several copies of the same file, and more
data than can fit on a CD-ROM. (UNIX users can think of these files as
Support for creating such a disc is uncommon.
VideoCDs often appear to have individual files that are 700MB or more.
In this case, they really *are* that big. They're written on separate
tracks in a special format (CD-ROM/XA Mode-2 Form-2) that drops error
correction in favor of more space. This works fine for video data, but
is definitely not recommended for ordinary data. Copying the files may
not work on some systems (e.g. you can open the files from Windows but
may not be able to from Linux).
If you want to duplicate a CD-ROM, you should use the "copy CD" feature of
your recording software. Some software is more capable of dealing with
complex CDs than others, so if you have a particular kind of CD in mind
(such as VideoCD) you should check the capabilities of the software before
making a purchase.