How to patch FAT32 boot sector External links Options

[ktp]

Hello,

I remember reading an article about patching FAT32 boot sector (by setting 3 or 4 NOPs to the boot sector code) in order to fix MS boot sector code. In U_SET_XP program the wording is "CHS knockout".

I desperately searched using Google/BootLand but could find again this article :-(.
What I need is to know the old binary values to be patched, and the new values (NOPs).

Thank you.

[was_jaclaz]

Here :
http://www.911cd.net/forums//index.php?sho...1702&st=129



jaclaz

[ktp]

Thank you Master jaclaz for your quick answer !

[was_jaclaz]

Thank you Master jaclaz for your quick answer !

You are welcome.

jaclaz

[ktp]

For the records :

FAT32 boot sector ("MSWIN4.1" or "MSDOS5.0" found starting at address 0x03) :
At address 0xE6, 4 bytes 0x0F, 0x82, 0x4A, 0x00 => patched to 0x90 0x90 0x90 0x90

NTFS boot sector ("NTFS" found starting at address 0x03) :
At address 0xD9, 4 bytes 0x0F, 0x82, 0x3A, 0x00 => patched to 0x90 0x90 0x90 0x90

With this patch, I think I can solve my booting problem with my mp3 player :
http://www.boot-land.net/forums/index.php?showtopic=8493

Now I will go to experiment with this !

[was_jaclaz]

With this patch, I think I can solve my booting problem with my mp3 player :

I cannot see how it could be related to it.

From what you posted, your only hope is finding a way to have makebootfat (or it's principles, i.e. double or triple use MBR, as tinybit suggested) working.

http://www.boot-land.net/forums/index.php?showtopic=7507

jaclaz

[ktp]

@jaclaz

The problem is that I cannot use MBR : the mp3 player (= USB key) has only boot sector (in other words either you select under HDHacker boot sector for E: or Physical drive 1, the content is the same).

Originally the mp3 player came with an almost nulled (all zeroes) boot sector (no boot sector code, only the 55AA and few signature bytes at start). After formatting to FAT32 with XP, and patching the boot sector, I still have the "Disk error, Press any key to restart" message. chkdsk gives no problem, and the mp3 player works fot its music functions.

I understand that triple MBR assumes MBR, or in my case no MBR is possible.

[was_jaclaz]

I understand that triple MBR assumes MBR, or in my case no MBR is possible.

Triple MBR assumes nothing.

You are assuming something.

The idea is to have some code that LOOKS to the BIOS and Windows as a MBR, but that can ALSO be seen as a bootsector (so that the MP3 thingie will still think it is a bootsector) and NO hidden sectors.
Or, if you prefer, a bootsector that has also partition data and disk signature.

Please try reading the above comparing it with this:

The problem is that I cannot use MBR : the mp3 player (= USB key) has only boot sector (in other words either you select under HDHacker boot sector for E: or Physical drive 1, the content is the same).

Doesn't it look strangely similar?

What if you actually READ:
http://www.boot-land.net/forums/index.php?...c=7507&st=5

AND this:
http://www.boot-land.net/forums/index.php?showtopic=761

AND links within the latter?

Then, once you have got the hang of it, you can start experimenting with either makebootfat or tinybit's solution.

jaclaz

[ktp]

@jaclaz

Thank you for your help. I tried makebootfat using your mkboot.cmd batch file. But as soon as I replug the mp3 player it automatically does a "Memory checking", which results in an automatic reformat of the USB key to factory mode by the player itself. The bootsector is reset to almost null as said previously.

Edit: if I install grub4dos to it, I got "disk error" message too from grub4dos boot code.

So the only boot sector it seems to accept is FAT32 boot sector, but then my BIOS could not boot it (Disk error), even after patching with 4 NOPs as said. So the problem is why the boot sector code cannot read the ntldr on the disk.

[was_jaclaz]

I tried makebootfat using your mkboot.cmd batch file. But as soon as I replug the mp3 player it automatically does a "Memory checking", which results in an automatic reformat of the USB key to factory mode by the player itself. The bootsector is reset to almost null as said previously.

Edit: if I install grub4dos to it, I got "disk error" message too from grub4dos boot code.

So the only boot sector it seems to accept is FAT32 boot sector, but then my BIOS could not boot it (Disk error), even after patching with 4 NOPs as said. So the problem is why the boot sector code cannot read the ntldr on the disk.

NO.
The whole point is NOT that one.

The point is that even if you make it load NTLDR, any Windows NT based system WON'T boot from the stick, as it would miss Disk Signature and thus you won't have a valid arcpath.

Sure makebootfat won't work "as is", but maybe you can manually use it's "short MBR".

• Format the stick as FAT32 (with NO partitions, as superfloppy).
• Try using it as MP3. Make sure that the MP3 function does not change anything.
• Post the bootsector.

jaclaz