Complex sentence: RollBack Rx installs to the hard drive's master boot record, which loads prior to the Windows operating system, which allows the hard drive to be reverted to a previous snapshot state even in the event that Windows is unable to boot.
Split into simpler sentences: RollBack Rx installs to the hard drive's master boot record, which loads prior to the Windows operating system. This boot priority enables RollBack Rx to revert to a previous snapshot state even in the event that Windows is unable to boot.