To compile DGD on Win32, you'll need Visual C++ 4.0 or newer.  Simply
double-click the file windgd.mak to start.

There are some caveats for compiling with Visual C++ 6.0 and later: first,
you'll need the Professional edition.  Second, the safe optimizations
selected for VC 4.0 are apparently translated into unsafe ones for VC 6.0.
Either turn off optimization, or experiment with the settings until you
find a good set.