The Creative Suite 4 installer installs fonts into a default system font directory. Many of these fonts are newer versions of fonts installed by Creative Suite 3. If the installer finds older versions of these fonts in the default system font directory, it will de-install the older versions, and save them to a new directory. The default system font directory is:
Apple Macintosh: <System Disk>/Library/Fonts
Windows: <System Disk>:\Windows\Fonts
The older fonts will be saved in the new directory:
Apple Macintosh: <System Disk>/Library/Application Support/Adobe/SavedFonts/current
Windows: <System Disk>:\Program Files\CommonFiles\Adobe\SavedFonts\current
This new directory will also contain a file named "ReadMe.html" which lists the saved fonts, and the version numbers of the new and of the old font files.
You can re-install the older fonts by deleting the new font files from the default system font directory, and moving the old files back into that directory.
There are additional fonts on the installation disk. For information on installing these fonts, see http://www.adobe.com/go/learn_fontinstall_en.