[ciderpunx]

In the syscall docs under "C A V E A T P R O G R A M M E R"

  > Certain structures,  constants  and  system  calls  below 
  > are   private   to   the   DOS    and    are    extremely 
  > version-dependent.  They  may  change  at any time at the 
  > implementors' whim.

That pretty much summarises my experience of trying to work with Microsoft products. Arbitrary, undocumented API changes every time the version number changes "at the implementors' whim".