Windows system32 directory should be left as one of the PATH variables.
PATH=D:\GRASS-64\etc;D:\GRASS-64\etc\python;D:\GRASS-64\lib;D:\GRASS-64\bin;D:\GRASS-64\extralib;D:\GRASS-64\msys\bin;D:\Python27;D:\Windows\System32
PATH=D:\GRASS-64\etc;D:\GRASS-64\etc\python;D:\GRASS-64\lib;D:\GRASS-64\bin;D:\GRASS-64\extralib;D:\GRASS-64\msys\bin;D:\Python27;D:\Windows\System32