Question about HD Partitions

[Ponch]

oops,... apparently it is not that simple. Maybe first try it on a test disk. The first thing to do is to write down on a paper where your partitions start and stop (cylinder, head and sector). Once you've wiped the MBR, you have to rewrite it and to recreate your partitions without formatting else you lose your data for good. I can't try it myself right now as I have boot manager in my mbr and it racts differently. And there is nothing to gain from it. Wiping the MBR is not deleting it. I mean you don't regain any disk space, as already stated by McTavish. It is playing with fire, big risk, small reward. And it's got nothing to do with this forum.

Edited...

I just tried, this is not for the faint harted. Also no warranty by me (multiboot or XP not starting).

Wanna wipe it ? -> Wipe the MBR with "E" (erase), rewrite it as Standard IPL, and press F2 (get "partition was written" message), go stand on each partition and press F2. Reboot and you'll see ...no difference at all.

Edited December 28, 2006 by Ponch

[jaclaz]

Hey people, it's not "black magic", it is just editing a few bytes.

Bootcode goes from offset 0 to 445 (first 446 bytes of the 512 bytes MBR).

Partition table goes from offset 446 to 509 (subsequent 64 bytes)

"Magic" bytes (OK, I lied ) 55AA hex MUST remain (last 2 bytes)

If the system is used under 2K/XP/Server2003 an additional part must be kept, the "disk signature" that is 4 bytes long between offset 440 and 443.

The 2 bytes at offset 444÷445 are normally ALREADY 00 (zeroes).

So, all you need to do is to write 00's to the first 440 bytes of the MBR (offset 0÷439).

This can be easily made with an hex editor.

If you need a command line or script :

Just get dsfo from the DSFOK package and run:

dsfo \\.\PHYSICALDRIVE1 0 512 C:\backmbr.ori

this will backup the MBR of drive 1 to file.

fsz c:\1stpart.mbr 440

this will create a 440 bytes long file filled with 00's.

dsfo C:\backmbr.ori 440 512 c:\2ndpart.mbr

this will extract the last 72 bytes from backup of original MBR

copy /B c:\1stpart.mbr + c:\2ndpart.mbr c:\emptymbr.new

this will assemble the two parts in a new 512 bytes file

dsfi \\.\PHYSICALDRIVE1 0 512 c:\emptymbr.new

this will copy the new MBR to the drive

(change number of drive where appropriate, DO NOT use PHYSICALDRIVE0, it is the BOOT drive)

Though the aim of setting to 00 a number of bytes that are never read (if the drive is not the boot one) escapes me.

Now, if you would have talked about reusing the other 62 unused (hidden) sectors of first track, that could be another thing, though given the size of current drives the avaibility of some additional 62x512=31,744 bytes still does not look to me as a great deal....

jaclaz

[McTavish]

Sure it’s no big deal jaclaz if you know what you are doing. If you just take your time with a disk sector editor and understand where the disk signature is, you can zero out everything before it. But as you said, what’s the point. Personally I always have a bootmanager installed in the first track of every drive, so that I can swap drives around and still boot all my OSes straight away.

The Disk Signature has been around since NT3.5 and has been a component of every WinNT OS ever since – even Vista. In fact it has a new significance in Vista.

http://www.multibooters.co.uk/mbr.html