What can Windows 8 Pro downgrade to?
If you bought a PC with Windows 8 Pro preinstalled you can downgrade to either Windows 7 Professional or Windows Vista Business.
Also, in case you're wondering about the differences between Windows 8 and Windows 8 Pro, know that the Pro version offers several power user and enterprise-centric features such as BitLocker disk encryption and the ability to boot from a virtual hard drive (VHD). PCWorld detailed the features in each Windows 8 edition in April.
What do I need to downgrade?
To take advantage of your Windows 8 Pro downgrade rights, you need installation media (such as DVD or USB key) for Windows 7 Professional or Windows Vista Business. You also need a valid product key for the older OS. Microsoft says it's fine to use a product key currently in use on another machine; you just need the old code to get past the product key request during installation.
Where can I get the installation media?
The tricky part is obtaining installation media for Windows 7 Professional and Vista Business because you are pretty much on your own for sourcing installation discs. You can try calling the manufacturer of your Windows 8 Pro PC to see if they will give you the Windows 7/Vista installation media you need, but don't get your hopes up. Posing as a regular customer looking to buy a Windows 8 Pro machine, PCWorld called the home and home office sales lines for Dell and HP. Both companies said they do not supply downgrade discs for free or at a nominal cost. Dell, however, will sell you a downloadable version of Windows 7 for about $290. You also won't get downgrade discs directly from Microsoft, and if you don't have the disc, you can't downgrade.
Again, downgrade rights are largely designed for businesses that may have Windows 7 installation discs on hand or have volume licensing agreements that provide access to older versions of Windows.
I have the right installation disc and a product key, now what?
If you have installation discs for Windows 7 Professional or Vista Business, you are almost ready to downgrade. As with any Windows installation, make sure any personal files already on your PC are backed up on a portable hard drive or an online backup solution. You should also make sure that you have Windows 8 installation media for when you want to move back to Windows 8. New PC owners should pay attention during first-time startup of a Windows 8 PC for a prompt to create system recovery discs. Otherwise, you can use Microsoft's built-in tools in Windows 8 to create a system image or recovery media .
TIP: PCWorld's sister publication Computerworld points out that you may have to disable the new Windows 8 secure boot feature in your Windows 8 machine's BIOS settings. To do this go to the Charms Bar in Windows 8 and select Settings > Change PC Settings > General > Advanced Start Up. On the next screen select Troubleshoot > Advanced Options > UEFI Firmware Settings (this option is available only on new Windows 8 machines).
Once you're set to downgrade, just pop in your Windows 7/Vista installation disc or USB drive and install the system as you normally would. When prompted for a product key, use the Windows 7/Vista key that came with the older OS' installation discs and not the newer Windows 8 key; however, you will need your Windows 8 key after Windows 7 is installed.
Regular online activation for Windows 7/Vista will fail because you used a product key that is already in use or was in use at a prior date on a different machine. So now you have to activate your Windows 7 downgrade installation by telephone.
Your computer should automatically alert you that online activation failed. If it doesn't you can manually activate your machine in Windows 7 by clicking Start > Control Panel. In the search box of the Control Panel window type “activate” and hit enter. Click the link to “Activate Windows.” When you try to activate online, the process will fail and you should see a window with a bunch of empty text entry boxes as well as a phone number for the Microsoft helpline.
During the helpline call you may have to speak with a customer representative. Just explain the situation and have your Windows 8 Pro product key available to prove your PC has downgrade rights. You will then be given a single-use activation code (usually it's annoyingly long) to enter into the activation window. Once the code is entered and confirmed, you're all done.
If you have more than one Windows 8 PC that you need to downgrade, Microsoft says you can just use the same Windows 7/Vista installation media on each machine.
Downgrading from Windows 8 Pro to Windows 7 Professional or Windows Vista Business is not a simple process, but at least the option is there if you really need it.