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Boot Sectors
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Boot Sectors

Windows 95 Boot Record

This boot record boots Windows 95 (DOS 7.00) from a FAT12 or FAT16 partition. This boot record is located in the first sector of a physical primary DOS partition on a hard disk drive, or the first sector of a floppy drive.


This is a ZIP archive that contains the Win 95 boot record source code and some batch files to construct the boot record.

This contents of this ZIP archive are:
  • W95PBR.ASM - Win 95 boot record source code (see below)
  • MAKEFILE.BAT - Batch file to assemble/link/extract
  • VERCODE.BAT - Batch file to verify the code
  • W95RAW.BAT - Batch file to extract and dasm the boot code using DEBUG
  • W95RAW.CMD - DEBUG commands used by W95RAW.BAT


This source file can be assembled, linked, extracted, and written to your hard drive as real working boot code. Click on the heading to view the file.

There was an oddity with this code. At 7CDE there is a CMP AL,0D8h instruction. This compares the lower 8 bits of the IOSYS address. I could not get that to assemble correctly. I'm sure its just a syntax problem - maybe I should read the manual (if I had one)!


This batch file assembles, links, and extracts the boot code. W95PBR.ASM is assembled with MASM version 6.11d into W95PBR.OBJ. W95PBR.OBJ is linked with LINK version 5.31 into W95PBR.EXE, W95PBR.EXE is processed by the BOOTEXE utility into W95PBR.BIN.


This batch file verifies the new boot code with what's in the actual boot record, or what's in a file. Customize to your preference. Note that not all assemblers work the same - some add slack bytes (nop's), other's don't.


This batch file uses DEBUG to disassemble the raw boot code. The DEBUG commands are in the file W95RAW.CMD. The DEBUG output is then processed by the DBLFIX utility to clean it up.

Utility Programs

Utility programs used by this archive are: You can get more info on these utilities and others by following the above links.

See Also

Lance Costanzo, [email protected]