On the blender.org Download page it only says 64 bit installer. I have a Windows 7, 32 bit computer and OS.
Here it is:
Blender 2.78c Windows 32 bit Download (clicking this link will start the download)
To find it in the future, click on the "macOS, GNU/Linux, and other versions" button to find alternate versions, including 32 bit versions.
Hope this helps.