Article: " At the very top of the registry entries is "Computer." Click on it to select it. From the header menu, choose "File" then "Export." The whole registry will be exported into a text file. Navigate to the folder where you want to save your backup then type in the name of your registry file. When you're done, click on the "Save" button. Your registry will be backed up in that file with a .reg extension. If anything goes wrong with your modifications, you can always revert to this stable version. Take note where you keep the registry file you've just exported in case you want to undo your changes later. It is always advisable to backup your registry before doing anything to it.

What is a summary?
Select "Computer. Export registry. Note the registry file.