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MERCURY127

[solved] There is any really WORK way to forbid 98SE installer write to MBR boot area?

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13 hours ago, MERCURY127 said:

I not think that installer use fdisk for write mbr...

Which is good, so that or similar sequence of bytes is likely to be *in some other file*, as said (check point #3 above).

The technique used to store the sequence of bytes is very likely to be similar. 

jaclaz

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solved. :D

D:\IF1808>fc /b SUWIN.0 SUWIN.EXE
Сравнение файлов SUWIN.0 и SUWIN.EXE
0001F46E: 75 EB
0001F4CA: 74 EB

WARNING:
possible obvious side effects...

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Posted (edited)

Good. :)

In the meantime I checked (only out of curiosity) with gsar the expanded contents of the first files on win98 SE install (up to base4.cab) and besides the matches (9)  in FDISK.EXE, there is ONLY a match for SUWIN.EXE:

suwin.exe: 0xe6c2
suwin.exe: 1 match found

and there the MBR is in its "expanded" 512 bytes form (though still missing the error messages) between a copy of the FAT12 (/16) and a copy of the FAT32 bootsectors.

The error messages are a little past that at 0xEEDF in the form of strings "queerly" separated by Hex 24 character :w00t:.

jaclaz

 

 

Edited by jaclaz

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12 hours ago, jaclaz said:

The error messages are a little past that at 0xEEDF in the form of strings "queerly" separated by Hex 24 character

The Hex 24 '$' characters are the end of string delimiter used by DOS Calls such as INT 2109.

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8 hours ago, rloew said:

The Hex 24 '$' characters are the end of string delimiter used by DOS Calls such as INT 2109.

Yep :), but it remains "queer" because usually in MS programs (including FDISK) the strings are 00 terminated, in FDISK,  there is - besides the 00 separator - a field for length of the string, as described by the given link, which - while being different from "normal" C programs string storage - makes (to me at least) more sense as this "length" field most probably simplifies the command used to write it.

jaclaz

 

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Posted (edited)

I pinged Daniel B.Sedory (The Starman) about the topic and he plans to make a page similar to :

https://thestarman.pcministry.com/asm/mbr/WTC.htm

but related to "where is the code" in 9x.

For the moment he quickly checked a few more files and found another other copy of the MBR code in OEMSETUP.EXE.

While the files tffsprop.dll and tformat.exe contain a copy of the "Standard" (since MS-DOS 3.30 and up to 95 A) MBR code:

http://starman.vertcomp.com/asm/mbr/STDMBR.htm

jaclaz

Edited by jaclaz

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