What is a disassembler?
A disassembler is a computer program which translates machine language into assembly language, performing the inverse operation to that of an assembler. A dissasembler differs from a decompiler, which targets a high level language rather than assembly language. Disassembly, the output of a disassembler, is often formatted for human-readability rather than suitability for input to an assembler, making it principly a reverse-engineering tool. Though this may not do you any good unless you know assembler already.