Once upon a time I used to swear by registry backups using a tool called ERUNT, which sadly quit working with Windows years ago. At the time I couldn't find a replacement, so I just said "Oh well" and forgot about it. Then the Start Menu on my wife's PC broke this weekend. It had happened to me once before and I got lucky -- you add another user profile, and if it works, the problem isn't Windows proper but in the registry -- and when I added the 2nd user my account started working, so I just had to delete that 2nd account. I didn't get lucky with her PC. Rather than try to duplicate EVERYTHING tied to her account for that new one, I restored a full image backup. It worked, but it was kinda like using a sledgehammer to open a pistachio. So I went looking for a registry backup app, again, and found 2 that work, though neither do everything that ERUNT used to.

Tweaking.com Registry Backup Portable copies the files making up the registry to a folder while preserving the original folder names & hierarchy. I liked that part because if a copy of Windows wouldn't start, I could boot to my Windows To Go drive or a WinPE USB stick and manually copy the files where they belong. What I dislike is that it uses a couple of Active X files -- Microsoft's been trying to end Active X, and my guess is that the app will stop working at some time in the future. For now though, testing in a Win11 25H2 VM it works.

tweaking[.]com/features/registry-backup/

Registrar Registry Manager comes in free and paid versions, and while I was just interested in backing up the registry, it has several editing features. You can also run it from the command line, e.g., use Terminal. It does appear to be a more professional app than the one from Tweaking[.]com, it has its tradeoffs. Backups are stored by default in a folder inside C:\Users\ -- you can specify another folder, but when I tried that it skipped one of the big registry files. It also does not preserve the original folder structure, so you'll have to remember [or search] for where to copy them manually if Windows won't run. And you've got a shareware nag to click through whenever you open the app. The link below leads to the site's home page, because that's where you'll find, and need to download the Registrar Registry Manager temporary fix, which is a Zip file with 2 files you have to copy into the program's folder for it to work in Win11 24H2 or 25H2.

resplendence[.]com/main

You can of course always set a Restore Point, and sometimes they will actually work when you need them to, but I haven't had the best of luck with them so depend on them at your own risk. Microsoft says you should just export the entire registry using Regedit, which is a method that IMHO is at best a joke. Every week or so [maybe more often?] I'll just back up the registry, then save the 7-zipped file next to the image backups.