There are some confusions while need simulation MSP430 by Proteus because it needs *.hex - file or *.cof - file. Following some partner of this forum suggest that change the output file *.out into *.cof ---- This is enough to purpose. Here I make a small tip to do that change automatically.
From the Project Explorer, right click on active Project folder, you next choose following command: Show Build Settings... \ Build \ MSP430 Linker \ Basic Options. In the right side, you will see the line "Specify the output file name" and next is textbox with contente : "${ProjName}.out". Now, you change it into "${ProjName}.cof"; all click ok. and Ctrl+B to rebuild your Project and enjoy.
How interesting! :D.