How to revert to Windows 7 after installing Windows 8?

You can't uninstall the Windows Developer Preview. To reinstall your previous operating system, you must have restore or installation media.

See "Notes about Installing The Developer Preview"

http://msdn.microsoft.com/en-us/windows/apps/br229516

You may have a "windows.old" folder on the C drive, this will contain all your files that were in the W7 installation, unless you formatted the partition prior to installing W8.

As @Moab said

You may have a windows.old file on the C drive, this will contain all your files that were in the Windows 7 installation, unless you formatted the partition prior to installing Windows 8 Developer Preview.

Using this article from Microsoft support you can recover data from windows.old file. The summary for the article says

This article describes how to manually restore a previous Windows installation on the computer to replace the current Windows Vista installation.

To do this, you must use the command prompt, and you must type specific commands at the command prompt to rename and to move folders between the different versions of Windows.

This article is intended for a beginning to intermediate computer user.

The article is intended for Windows Vista, but you can follow the steps and see if it still applies for reverting from Windows 8 Developer Preview to Windows 7.

GOING BACK TO WINDOWS 7 from WINDOWS 8

As an engineer, I was curious about Windows 8. Thus I bought Windows 8 online directly from Microsoft which automatically was setup on my USB thumb drive. I did a BIOS update on my computer, also saved an image of my Windows 7 system (VERY SMART STEP!) and then I was ready. I choose to do a clean windows 8 install! Played with Windows 8 for a month and realized what a mess.

So then, I thought, its time to put Windows 7 back on my computer. This should be simple. Just restore my Windows 7 image. WRONG ! ! ! !

You have no idea how many problems and errors I discovered. There were so many I did not even keep track of all the error codes and everything that would not work. And I was armed with everything: I had a Windows 7 bootable USB recovery drive, a Windows 8 bootable install/recovery USB drive, a Windows 7 image file, and the latest and greatest BIOS. All were of no help !

What I discovered was that Windows 8 changes your hard drive from MBR to GPT (boot sector) and each one does not like the other. Thus you CANNOT boot a Windows 7 recovery USB drive AND/OR do a Windows 7 image restore if your hard drive is set as a GPT volume/disk; likewise, you CANNOT do a Windows 7 MBR image recovery from a Windows 8 recovery bootable USB drive.

After spending 16 straight hours of research and work on this problem, I finally found the solution. It's a painful solution but it works.

What I had to do is: (this assumes you installed Windows 8 and thus your hard drive is set as GPT)

see: http://www.sevenforums.com/tutorials/26203-convert-gpt-disk-mbr-disk.html

• boot up from your Windows 8 recovery/install USB drive and enter into COMMAND PROMPT (NOTE: this is not starting up the entire Windows 8 operating system)
• you MUST manually delete all volumes on the primary disk that is listed on your hard drive (do research using 'diskpart' and also 'delete partition' and 'delete volume' commands. I think I finally had to use the delete partition command)
• Then execute a 'convert mbr' command to the primary disk

Once you know that GPT is gone, your set! Just reboot using a Windows 7 recovery USB/CD drive and select restore an image (Windows 7 image). It works! You now have Windows 7 back.

You could try using the original Windows 7 install CDs, but my new laptop does not have a CD player.