Due to architecture changes in the 64 bit window 7 machines, you are no longer able to install 32 bit SolidWorks on a 64 bit machine. The installation manager will not allow you to even attempt the install.
This is only possible with Windows XP Professional x64 Edition operating system. The 32-bit version of SolidWorks cannot be installed on the 64-bit versions of Vista or Windows 7; the 32-bit Installation Manager blocks the ability to do so with these versions.
These rules apply to all SolidWorks releases.