I downloaded Firefox 4 setup by using the Firefox 3.6.x Update feature and saved it as a file. I was not offered any choice as to whether to install a 64-bit or a 32-bit executable. It also did not tell me whether the program that would be installed is 64-bit or 32-bit. When I run the downloaded file, I select the custom configuration of the cook-book vanilla installation routine. The default installation location is C:\Program Files (x86)\Firefox -- which is the Windows 7 directory for 32-bit executables. So, it would appear that Firefox 4 is 32-bit software, at least the one that I downloaded. I cannot find a download location on the Mozilla.com web site which is identifed as for getting 64-bit software instead of 32-bit. From which web site and page (URL please!) can I download a 64-bit version of Firefox 4?