Looking at the hardware and software requirements for SQL Server 2008, 2008 R2 and 2012 from Microsoft site, we should be able to install 32-bit version of SQL Server onto 64-bit (x64) Windows operating system.
If you have installation media or ISO image that contains both 32-bit and 64-bit version of SQL Server 2008, 2008 R2 or 2012, here’s how you can install the 32-bit SQL Server on 64-bit Windows (x64). When you insert the installation media, or mount the ISO image, in some cases you might need to double click on the setup.exe, you will be presented with the SQL Server Installation Center. Click on the Options link on the left.
You should then be able to select to install the 32-bit (x86) of the SQL Server.
You can kick off the 32-bit installation process, by running the following command:
setup.exe /action="install" /x86=true
As a matter of fact, you can use the X86=true in the command line or answer file if you want to have unattended installation of SQL Server 2008, 2008 R2 or 2012.
Once it has been installed, when you check the SQL Server version using:
For SQL Server 2012 installation, you should get something like the following:
Microsoft SQL Server 2012 - 11.0.2100.60 (Intel X86)
Feb 10 2012 19:13:17 Copyright (c) Microsoft Corporation Enterprise Evaluation Edition on Windows NT 6.1 <X64> (Build 7601: Service Pack 1) (WOW64)
Noticed that it is WOW64 (Windows 32-bit on Windows 64-bit).