The short answer is yes, if regedit.exe is in the image(s). You will have to disable the Write Filter in the OS before any changes can be made. For WES7, this could be EWF (ewfmgr.exe) or FBWF (fbwfmgr.exe). For Windows 10, it would be UWF (uwfmgr.exe). If there are domain policies in place, you might want to remove the terminal from the domain and access the system in a local account.
Contacting Dell directly about their product would be a better avenue to get a definitive answer.
Weather you can create a backup of the registry key might be a question. What is the problem you're looking to solve?