To nie wygląda na składnię NASM-a. Raczej na tandem TASM+TLINK.
Do nasma to trzeba by kod przerobić...
[bits 16]
segment code
..start:
mov ax,data
mov ds,ax
; ...
mov ax,4C00h
int 21h
segment data
; ...
segment stack class=stack
resb 4096
C:\pp\myprogs\asm>nasm dos.asm -f obj
C:\pp\myprogs\asm>wlink file dos.obj
Open Watcom Linker Version 1.9
Portions Copyright (c) 1985-2002 Sybase, Inc. All Rights Reserved.
Source code is available under the Sybase Open Watcom Public License.
See http://www.openwatcom.org/ for details.
loading object files
creating a DOS executable