If you want to install the Windows 7 RC candidate and not lose all your customizations then follow one of the two methods described below:

Method 1:

1. 1. 1. 1. 1. Download the ISO as you did previously and burn the ISO to a DVD.
            2. Copy the whole image to a storage location you wish to run the upgrade from (a bootable flash drive or a directory on any partition on the machine running the pre-release build).
            3. Browse to the sources directory.
            4. Open the file cversion.ini in a text editor like Notepad.
            5. Modify the MinClient build number to a value lower than the down-level build. For example, change 7100 to 7000.
            6. Save the file in place with the same name.
            7. Run setup like you would normally from this modified copy of the image and the version check will be bypassed.

Method 2: The official way of updating Windows 7 Beta to Windows 7 RC is the following:

1. 1. 1. Starting with a data backup. This includes documents, multimedia files and any other data or files that got created by the user and need to be transferred to the new system. We would suggest to either copy the whole Windows 7 partition to a spare drive or be very careful when creating the backup.
      2. Using Windows 7 Easy Transfer to backup Windows 7 settings. Windows 7 Easy Transfer is part of Windows 7.
      3. Formatting the partition Windows 7 Beta was on.
      4. Installing Windows 7 release candidate.
      5. Using Windows 7 Easy Transfer to restore the settings of Windows 7 Beta.
      6. Reinstalling any third party applications that are needed on the computer system.
      7. Restoring data from the previously created backup to the computer system.

That is a long process which can take hours or more depending on the data and third party applications that need to be reinstalled. The release candidate will block the direct update from Windows 7 Beta to it.