CONFIG.MSI folder is a hidden folder on the root drive of Windows, usually Drive C. The folder is used by the Windows Installer process to install updates and patches. You will find Rollback Script Files used by the installer . A Rollback script file (.rbs) is always stored in the Config.msi folder on the disk where the operating system is installed (usually C:\). The Roll Back Files (.rbf) files are stored in the Config.msi folder located on the disk where the program is located. This can be any drive.