I would agree with Georg that there isn't anything we can do about this.
 I had someone try from the Windows XP command shell and: "dir" "/w"
reports that it can't run the combined command, where: dir /w works just
fine.

My conclusions are:

This is a bug in the Windows shell (which os.system hands the command to).

There is a work-around using "call" as pointed out by Jean-François

The subprocess module is a better match for this, as you pass a tuple to
make quoting unnecessary.

According to the os module documentation, using subprocess is
recommended in preference to using os.system().