When I downloaded through Internet Explorer it converted the .MIZ suffix to a .ZIP. To get it the mission to work you need to rename the file to .MIZ
I had further problems with Vista trying to rename the file. Through Vista Explorer it appeared I had renamed the file correctly to to tutorial01.miz but in reality the rename had called the file tutorial01.miz.zip
I had to resort to the DOS prompt to rename the file properly but then the mission worked.