Unix tools are your friends!  You can disassemble all files by using a combination of Unix commands.  These are easily available on Windows through [Cygwin][1].

    find $SYSTEMROOT -name \*.exe -or -name \*.dll -print0 |
    xargs -0 -n 1 dumpbin /disasm 

The first command finds all `.exe` and `.dll` commands. The second applies `dumpbin` on each found file name. You can redirect the output into a file, or you can modify the above sequence to write the output of each disassembled file into a different output file.  You can also replace `dumpbin` with your favourite disassembler.

  [1]: https://www.cygwin.com/