BTW, I should have said "IDA Pro Freeware". It's a free version of an interactive disassembler, so everyone can try it out.
I use
version 4.1 to disassemble executables. I think it handles DOS executables better than later versions, but I hate its text-based user interface, so I use
version 5.0 and its graphical user interface to process the output of version 4.1.