Where can I get a GCC/G++ compiler for my 64-bit Windows 7 machine?
http://www.google.com/#q=win64+gcc
No matter how often the download page moves around, that should find it for you.
At the time of this post, the top result (and correct download site) was http://sourceforge.net/projects/mingw-w64/
Since that time, the project has moved to http://mingw-w64.org/ and you can find the Windows install packages at http://mingw-w64.org/doku.php/download/mingw-builds, which is now one of the top Google hits also.