I'm sure I'm not the only one who has booted a machine to find the following message waiting for them:Windows could not start because the following file is missing or corrupt\\Windows\\SYSTEM32 ...

"Starting Windows...Windows 2000 could not start because the following file is missing or corrupt: \\WINDOWS\\SYSTEM32\\CONFIG\\SYSTEM. "You can attempt to repair this file by starting Windows ...

To fix boot issues, when they attempted to repair BCD in WinRE, the command failed to do so and displayed the following result: Scanning all disks for Windows installations.

The main subfolders of the System32 folder that normally occupy space are DriverStore, FileRepository, Config, drivers, winevt, catroot, Log Files, etc.