How to Create a Custom Refresh Image in Windows 8
“Refresh your PC” is a new feature in Windows 8. By default, desktop apps are removed when you refresh a Windows 8-based computer, unless you create a custom image. After you create a custom system image, the image is used as the refresh image. This means that any existing image or OEM restore image is not used when you refresh your computer. We recommend that only experienced Windows 8 users who understand the consequences of this behavior create a custom system image.
The space that is required to create a custom image depends on the number of apps that are installed on the computer and may exceed 5.0 GB. In addition, the custom image creation process may take a long time, during which you should not restart the computer. A percentage indicator lets you monitor the progress of the process.
More info can be found here