The Windows Installer records the original state of system and the the sequence of changes it makes during an installation. This behavior allows the Windows Installer to reverse an interrupted or unsuccessful installation.
A smart user can interrupt an installation, browse secure files, and record information about the internal state of the system.
To prevent this behavior, set the DisableRollback value name, a REG_DWORD data type, to 1. For a specific user, make the change at HKEY_CURRENT_USER\SOFTWARE\Policies\Microsoft\Windows\Installer. To prevent all users of a computer from interrupting an installation, make the change at HKEY_LOCAL_MACHINE\SOFTWARE\Policies\Microsoft\Windows\Installer.
NOTE: Implementing this hack will prevent Windows Installer from reversing an unsuccessful installation, which could render the system inoperable.
NOTE: A positive side effect of this hack is the reduction in the amount a freespace required to perform an installation.
This hack can be implemented by enabling the Disable rollback Group Policy at User Configuration\Administrative Templates\Windows Components\Windows Installer or Computer Configuration\Administrative Templates\Windows Components\Windows Installer.