If you were running Windows 7 and you upgraded to any of the preview releases of Windows 8, and you did not reformat (erase) your hard drive during the installation, you are still able to retrieve files from the previous operating system by looking into the Windows.old folder.
You see, by default, Windows during upgrades does not delete any files, instead it always moves the previous installation files, including users files, to the Windows.old folder. Knowing this it is possible to recover all your files without much complication.
Now there are 2 method, both pretty easy: First is by using a small application from Microsoft that automates the process and the second method is recovering those file manually. Keep reading to learn more…
The only thing is that you need to download and run a Troubleshooting Pack from Microsoft, which will automatically retrieve your personal files and then it will copy them back to their original location path. That is all!
Alternatively, you can do this process manually:
Go to Computer and access the Windows drive, usually C:\
Double-click the Windows.old folder. Here you’ll find a variety of folders, for this example we are going to be recovering users files, but in the same way you can go deeper into other folders and recover other files, e.g., certain program configuration files, portable programs, etc.
Double-click Users and then select the username from which you are extracting the files.
Then just copy and paste the files you want to either a portable hard drive (recommended) or to the same location in Windows 8.
Repeat these steps 3 and 4 for each user account in your PC.
Even though going back to a previous version of Windows isn’t officially supported in Windows 8, it still something possible to do; check this previous article — How to uninstall Windows 8 and restore Windows 7 [Step-by-Step].