Reply To: Where are the default powershell environment variables physically stored?

After taking your lead and some further research, it seems that powershell is getting these default values out of the registry, as I suspected:
HKEY_CURRENT_USER\Volatile Environment for User environment variables
HKEY_CURRENT_USER\Environment for System environment variables
HKEY_CURRENT_USER\Software\Microsoft\Windows\Explorer\User Shell Folders

and elsewhere!

Thanks Dave!