There is no 64-bit builds of Firefox for Windows from Mozilla yet. The 32-bit builds works on windows 7 64-bit.

Besides if you were to use a 64-bit build of Firefox you would need 64-bit Plugins also.

thanks James

I kept searching and I stumbled upon the pre releases.

there was a page and it said there is a 64 bit firefox "nightly" that I can install and run.

I have it installed now and it is nice so far.

The Nightly you found I figure is fpor what lead to being the unstable Firefox 10.a1 nightly builds that gets one or even two updates (due to respin) each day due to checkins and are not meant for regular Firefox users but rather developers and testers in mind. The page even has the note of "These builds are for testing purposes only".

Link to 64 bit of Nightly http://nightly.mozilla.org/

edit: Fixed linked it was linking to the tinderbox hourly builds (multiple builds a day) which can be much more unstable if the build did not build properly (due to checkins and trying stuff) and yet may still be green and uploaded. Use the /firefox/nightly/latest-trunk/ not tinderbox if you must.

Also note the unstable Nightly builds get updates each day (sometimes a respin even) and are not meant for regular Firefox users in mind but devs and testers who at very least understand the basics of separate installs and separate Profiles for each.