Updating master boot code
However, if needed, you can specify the /force option, which causes a forced dismount of the partition if the standard lock attempt fails.
When using this option from Win PE it shouldn't cause any problems, but caution should be used when using it in Windows since it can cause unexpected behavior as all open file handles on the partition are invalidated.
In "Adding Windows PE to Your Windows 7 System," I showed you how to install an "onboard emergency kit" for repairing a non-booting system.
But sometimes that kind of wipe-and-reimage process isn’t enough: The OS might be there—it just can’t boot.
Clearly, in the retrofitting, the author wanted to save a bit of coding—thus, the volume-letter-points-to-drive-number circumlocution.
If possible, it's recommended to use the version of bootsect that matches (or is newer than) the version of Windows being repaired.
For example, use the Windows 7 version to repair a Windows 7 or Vista boot sector. Also note that you need to use a compatible version when running in Windows.
The BIOS loads both code and table into RAM, then executes the code.
If the code is damaged (or just zeroes), the code execution will either bluescreen or hang the system.
As a result, this method will not work from a booted Windows system.