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

"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 ...

In the file monitor log after the installer starts to rollback i notice something is written to this file C windows\system32\config\software.log I think the files in here are used by the event log ...

Windows stores its Event Viewer’s logs in C:\WINDOWS\system32\config\. You can open File Explorer and navigate to that location to access the log files.