System Restore is a Windows safety net: it rolls the system back to an earlier saved state — a restore point — to undo a bad update or installation. Because of what it touches, it can quietly affect some hardware identifiers.
What System Restore actually does
System Restore is not a full backup of your files. It captures and restores a specific set of things: Windows system files, installed programs, and importantly the Windows Registry, as they were at the moment a restore point was created. When you run a restore, those are rolled back; your personal documents are generally left as they are.
Why the registry part matters here
The registry is the relevant piece. Several software-level hardware identifiers live in the registry — the machine GUID being the well-known example. If a restore point was created before some registry-based identifier was changed, restoring to that point can roll that identifier back to its earlier value, because the registry as a whole is being reverted. It is not that System Restore targets identifiers — it is that the identifiers are stored in the registry, and the registry is what gets restored.
What it cannot touch
System Restore operates within Windows, on Windows system state. So it does not reach anything below or outside that. It cannot change the motherboard's SMBIOS UUID or BIOS serial — those are in firmware. It does not rewrite a partition's volume serial. It does not touch MAC addresses in the network adapters. Everything outside Windows's own system files and registry is beyond what a restore point captured, and beyond what restoring one can undo.
The practical point
If you have changed registry-based identifiers and later run System Restore to an older point, do not be surprised if those identifiers revert — the registry went back, and they went back with it. And the reverse: a restore point is not a way to change firmware or disk identifiers, because System Restore never touched those in the first place.
The takeaway
System Restore rolls back Windows system files and the registry to an earlier point. Because registry-based identifiers like the machine GUID live in the registry, a restore can revert them as a side effect. It cannot affect firmware identifiers, volume serials or MAC addresses — those sit outside what a restore point captures.