Yes it does.

Which version? Someone said there was a version 4 that was supposed to work with Win 7 64-Bit, but has not been released as yet!

All release versions of Firefox on Windows are 32 bit and work on 64 bit Windows. Firefox 4 will also be only released in 32 bit for Firefox 4.

You can use the current release version (3.6.15) available from http://www.mozilla.com or the Firefox 4 release candidate available from http://www.mozilla.com/en-US/firefox/RC

Firefox 4 is currently scheduled to be released on March 22nd