Microsoft Office 2000 Rollback
Office 2000 allows you to rollback an installation of Office if installation unexpectedly quits before completion or you intentionally quit the installation process. This means that your previous installation of Office is restored to its original state even if you cancel Setup in the middle of overwriting your Office files.
Windows Installer accomplishes rollback by creating a rollback script. A rollback script is a file containing a linear sequence of operations to perform, such as file and registry updates, configuration information updates, user interface notifications, and state information for other operations. Each operation recorded in the rollback script is a direct response of an operation in the installation script. The following are some examples of what is reported in the rollback script:
Write a registry key If the registry key did not previously exist, describe how to remove the registry key. If the key already existed, then back up the existing registry key so it can be restored.
Install a file If a file did not previously exist in the folder, describe how to remove the file. If the file already existed, then back up the existing file so it can be restored.
Create a shortcut to a file If the shortcut did not previously exist in the folder, describe how to remove the shortcut. If the shortcut already existed, then back up the existing shortcut so it can be restored.
Rollback scripts are stored in binary format. This improves efficiency, avoids the need for parsing the file, and discourages manual editing of the file.
Where Are Rollback Files Stored?
Rollback script files (.rbs and .rbf) are backups of existing files. Files with a .rbs file extension are rollback script files and files with a .rbf file extension are backups of existing files, both are stored in hidden folders called Config.msi. The Config.msi folders are created when Msiexec.exe starts copying from the installation point. The rollback script file (.rbs) is always stored in the Config.msi folder on the disk where the operating system is installed. The .rbf files are stored in the Config.msi folder located on the disk where the program that is being backed up currently resides. This is done so there is no crossing of disks when backing up the program files. All rollback files and the Config.msi folder are deleted when the installation completes successfully.
Note: If Setup fails, because you lost power during Setup for example, and you run setup again and it completes successfully, the config.msi folder will be removed. If Setup fails to remove this folder you can manually remove it using Windows Explorer.