Step 1: you buy a Windows 7 disk with license key (if you don't have one).
Step 2: you boot from it and install Windows 7 32 bit (it will let you use the partition where Windows 8 or Windows 7 64 bit is located on, while formatting it)
Step 3: you download all drivers for all hardware that aren't on the Windows 7 disk
Step 4: you install those drivers
There's a small caveat: a desktop that is 'certified for Windows 8' and sold with Windows 8 is not sure to be able to run Windows 7. Read about the new UEFI in http://www.zdnet.com/windows-8-is-a-one-way-street-for-consumer-pc-users-7000007136/ and http://news.techworld.com/operating-systems/3410119/do-not-downgrade-new-pcs-to-windows-7-hp-urges-customers/
Be sure the BIOS of your PC supports "legacy mode" boot or Windows 7 won't work at all! That's called 'security'. Some say it's a deliberate move by Microsoft to ensure a fast and wide spread of their all-important Windows 8.
Is it possible to downgrade a new desktop harddrive from Windows 8 or Windows 7/64-bit to Windows 7/32-bit? How does it work?
If not, any suggestions where I might acquire a desktop harddrive with Windows 7/32-bit or no operating system?