I recently heard about a Windows 2000 registry tweak that lets you back up open files. Do you know anything about this registry change?

The tweak involves a change to a backup engine setting. By default, the HKEY_CURRENT_USER\Software\Microsoft\Ntbackup\Backup Engine\Backup files inuse registry subkey's value is set to 0 (disabled). You can set this value to 1 to permit the backup engine to lock files during backup and restore activities. Doing so lets you back up open files, but be aware that this setting can cause problems in WINS, DHCP, and DNS because the setting places a temporary lock on the files that those applications use.