How to Make the (bootsect.dos) file

MAKE THE BOOT SECTOR FILE

You must now make a BOOTSECT.DOS file from the boot sector of the DOS partition and store it on C:\ (i.e., in the root directory of the NTFS partition).

Note that you cannot simply copy a BOOTSECT.DOS file from another installation, because the boot sector contains an internal table (used to locate the root directory) that describes the physical layout of the drive and partition on which it was created, e.g., the number of heads, the number of sectors per track, the location of the partition in sectors from the start of the drive, the size of the File Allocation Table, etc. This physical information will not, in general, be correct unless you're copying it from a system with an identical partitioning layout on an identical hard drive (not just the same capacity, but the same number of cylinders, heads, and sectors per track).

To capture the DOS partition's boot sector, log on to your NT system as Administrator. Copy the following text into a new file called READ.SCR:

L 100 * 0 1
N C:\BOOTSECT.DOS
R BX
0
R CX
200
W
Q

...where the "*" in the first command is replaced by the number corresponding to the drive letter of the DOS partition. Use 2 = C, 3 = D, 4 = E, and so on (the letters are those assigned to the partitions when running under NT). As an example, if the DOS partition is drive letter E:, the command would be "L 100 4 0 1". Note that the partition number is entered in hexadecimal, so that drive letter J: is 9, K: is 0A, L: is 0B, etc.

Once you have made this text file, start an NT command prompt, change directories to the location of this text file, and run the DEBUG program as follows:

(debug <read.scr)

This will create the file C:\BOOTSECT.DOS from the boot sector on the DOS partition. If the DEBUG command reports any errors, check your text file carefully to see if you made an error in entering the commands.

You can verify that the boot sector was correctly written to the BOOTSECT.DOS file by examining the file with a hex dump program (or by using DEBUG). Look at the first few bytes and also at the last few bytes for the following strings:

First bytes           Last bytes            Boots Which Operating System
--------------------  --------------------  ----------------------------
MSDOS5                IO SYSMSDOS SYS       DOS
MSDOS5                NTLDR                 Windows NT
MSWIN4                WINBOOT SYS           Windows 95 

USING NT DEBUG TO VIEW THE BOOTSECT FILES

1. Start an NT command prompt.
2. Enter the command "debug c:\bootsect.dos" (or "debug c:\bootsect.w40").
3. At the "-" prompt, enter the command "d 100 L 100" to see the first half of the file.
4. At the "-" prompt, enter the command "d 200 L 100" to see the second half of the file.
5. At the "-" prompt, enter the command "q" to quit back to the command prompt.