Microsoft release Windows 8 Release Preview and provided options to upgrade from earlier versions of Windows like Windows 7, Windows 8 consumer or developer preview, Windows XP and Vista. If you were running Windows 8 Consumer Preview or developer preview and installed Windows 8 Release Preview and didn’t reformat hard drive during installation, Windows will retain files from the user account so that you can retrieve old files from Windows.old folder created during installation.
After the installation of Windows 8, go to desktop app and then open Windows Explorer. Now open the drive that Windows is installed on (typically, the C: drive). You will find folder named Windows.old inside tis drive. This is the folder where your files are stored from previous version. Open this folder and you can see the Users folder inside it.
Open the folder with your user name and open the folders that contain the files you want to retrieve. Copy and paste the files that you want from each folder to a folder in Windows 8 Release Preview. You should be able to retrieve files for all users from Windows.old folder.
If you no longer need this folder, you can also delete it as it occupies large amount of space based on your files.