If you delete the entire Windows registry, your computer will not start up. This is a serious problem because it can mean that your computer is not able to function properly. If this happens to you, you may have to take it to a mechanic or software engineer to fix it.

The Windows registry is one place that should be left well-enough alone, but just for the sake of argument, what would happen if you deleted the entire thing? Today’s SuperUser Q&A post discusses the possibilities in order to satisfy a reader’s curiosity.

Today’s Question & Answer session comes to us courtesy of SuperUser—a subdivision of Stack Exchange, a community-driven grouping of Q&A web sites.

Screenshot courtesy of Wikipedia.

The Question

SuperUser reader SkYWAGz wants to know what would happen if the entire Windows registry was deleted:

What does happen if the entire Windows registry is deleted?

cd %TMP% reg query HKCR> RegTest. txt reg query HKCU» RegTest. txt reg query HKLM» RegTest. txt reg query HKU» RegTest. txt reg query HKCC» RegTest. txt @pause && cls for /f “delims=” %%I in (RegTest. txt) do reg delete “%%I” /va /f

The Answer

SuperUser contributors Daniel B and StW have the answer for us. First up, Daniel B:

Followed by the answer from StW:

Regedit hangs as soon as I try to delete HKLM\SYSTEM. After resetting the VM (because I am lazy), I get the following screen (the operating system is Windows XP):

(Translation: “Windows could not start because the following file is missing or corrupt: \WINXP\system32\config\SYSTEM”)

So yes, deleting stuff from the registry will absolutely positively kill Windows. And unless you have a backup, restoring it is impossible.

Have something to add to the explanation? Sound off in the comments. Want to read more answers from other tech-savvy Stack Exchange users? Check out the full discussion thread here.

Such critical information is the list of device drivers needed for booting the system. This may include:

Disk drivers (Floppies, Hard-Disks, CDs, USB Devices, …) Bus drivers (IDE, SATA AHCI, …) File system drivers (FAT, NTFS, …) …

However, by default Windows stores a backup copy of the registry. If you have enabled System Restore, you can find such copies in the (hidden) System Volume Information Folder inside the root folder of the system partition. Additionally, even if you do not have System Restore enabled, Windows saves a backup copy of the registry in %WINDIR%\System32\config\RegBack.

You can manually copy the backup files into %WINDIR%\System32\config\ to restore the registry data.