a description of writing the mbr code with that is right here
If you use this command, TestDisk will overwrite the code area of your disk necessary for booting the operating system(s). This might be useful if your system doesn't boot at all, and you've tried everything else! See below for details on how this new MBR will function on your system.
IBM PC/Intel partition
If you use this command, TestDisk will overwrite the present code area of your Master Boot Record (MBR) and write the MBR signature (the Hex Word 0xAA55) to your drive's MBR sector. Beginning with version 5.7 of TestDisk, new MBR code was created specifically for TestDisk by Neil Turton (the author of mbr-install; version mbr-1.1.8 includes the source code for the TestDisk MBR). This change means that TestDisk is now 100% GPL (Open Source) code.
Versions prior to 5.7 overwrite the MBR code with a copy of the Standard Master Boot Record (similar to MS-DOS's fdisk with the 'undocumented' /MBR switch). For a fully-commented copy of this DOS standard (or 'Classic') MBR code, see An Examination of the Standard MBR (edited copy for CGSecurity.org; France) or An Examination of the Standard MBR (The Starman's web site).
The TestDisk MBR
If you use TestDisk to write its MBR code to the first sector of your hard disk, it will very briefly identify itself by displaying
TestDiskon the screen at boot up. The code is programmed to try booting up from whatever Boot Sector resides in the first partition of the drive. If that's not possible, you will then see a mini-menu displayed on your screen like this:
Pressing the 1, 2, 3 or 4 keys on your keyboard, will command the MBR to try booting up from any boot sector(s) it finds in the 1st, 2nd, 3rd or 4th partition table entries in the MBR sector. Failing to do so will simply repeat the TestDisk MBR menu on your screen each time it fails to boot. If you press the F/f keys on your keyboard, the MBR will try to boot up the system from a floppy disk in your first (
/dev/fd0) floppy drive.
In most cases, once you're able to boot up your drive's original OS again, you'll want to change the TestDisk MBR code back to whatever you were using before encountering a boot problem. Note: Be sure you know exactly how to do that before proceeding - you don't want to remove your Partition Table again!
Back to Running the TestDisk Program