I remember XP registry had the different hive files with BAK extension, like system.bak
Helped me to boot unbootable Windows installations few times by just booting with a rescue CD, renaming system to something else and renaming system.bak to system.
This.
In versions of Windows prior to like Win10 version 18xx, there was an automatic backup of the Windows registry stored in the event you needed it to fix the machine (you could actually use regedit to control the number of backup copies it kept). For some reason only known to the space cadets at Microsoft, they disabled the backup mechanism for this. Turns out you can mostly re-enable it, but it requires several steps editing the registry and you also have to create a Windows task scheduler task to actually trigger the backups now (where it used to be automatic).
Pain in the rear orifice if you actually need it like I did on that system the other day. The relative ran the CCleaner registry cleaner on it and (of course) it totally nuked the registry. Even a repair install didn't fix it -- had to do a new clean install since there wasn't a registry backup to restore. Suffice to say, CCleaner wasn't reinstalled (and I told him not to bring it back to me again if he installed it and nuked it again in the future).
Regarding Windows system restore, new Windows installs now by default do not automatically create restore points as it is disabled. If you have an older upgraded Windows installation and system restore was activated on it, that continued to carry forward to each new upgrade.
However, if you do a totally clean Windows install on a machine, SR will be turned off by default. I suspect they did this originally due to the limited capacity of then expensive past SSD boot drives. However, that isn't an issue with the cheap larger capacity SSD/nvme drives now - you just have to remember to re-enable it manually.