If you are using a 64-bit version of Windows: http://www.fastshare.org/download/Masm64.exe or http://rapidshare.com/files/324083249/Masm64.exe or http://pliczek.net/index.php?p=23608 (At the bottom is the button: "POBIERZ PLIK". I recommend this link.)
If you are using a 32-bit version of Windows: http://www.masm32.com/masmdl.htm