http://support.apple.com/kb/HT1846 Question is why not? And does it really not work? Without getting into an argument of the merits of 64 bit mode in Mac OS X, I think most agree that Windows 7 x64 is much faster than Windows 7 x32. I'm disappointed by this, especially since the computer was advertised as a 64 bit product. I think a reasonable person would interpret that to mean that it runs 64 bit OSes, but maybe not.