From the Sharepoint Blog,
With many users both on campus and at home opting to upgrade to Windows 7, I wanted to pass along a tiny tidbit of information. Windows 7 is available in 2 different platforms, 32 bit and 64 bit. Users opting for 64 bit should note that there are 2 versions of Internet Explorer installed.
When using internet Explorer, you should make note to use the link that says Internet Explorer, not Internet Explorer (64-bit). Using the 64 bit version can cause problems when accessing Sharepoint, like not being able to properly open Office files.