According to this Facepunch thread, the Quake III CD comes with a 16-bit "Autorun" launcher. (Windows refuses to run it since 64-bit x86_64 does not support running 16-bit code natively.) However, you can bypass the launcher and run DEMO32.EXE
directly, which contains the actual installation program; when prompted for a file, give it QIII.DBD
.
Method 1: If you MUST have a classic QIII/Q3TA installation
Instead of launching SETUP.EXE, just run DEMO32.EXE and a file open dialog should appear. Point it to QIII.DBD on the CD.
[...]
Remember to apply the 1.32 point release AFTER installing both Q3A and Q3TA. The official 1.32 point release is available from the official ID Software site - www.idsoftware.com
Method 2: Using ioQuake3
There is an engine update called ioQuake3. It's less buggy and more efficient than classic Q3 1.32
Install ioQuake3 first (http://ioquake3.org/get-it/) and then from the same page, grab the data installer as well. It will unpack your CD for you.
(KD007 on Facepunch)
In the earlier days of 32-bit Windows, many 32-bit programs would come with 16-bit installers (especially InstallShield) or at least having an initial 16-bit stage; one possible reason for this was to display a proper explanation message when the user attempted to install the program in Windows 3.x.