I am talking about Classic remix for Windows 7, a Windows 7 compatible theme that gives Toolbar buttons in style of Firefox 3.7 and contains graphics from the future Firefox 3.7 and Firefox 4.0 mockup.
Install the add-on from: https://addons.mozilla.org/en-US/firefox/addon/13579
To proper works you need these add-ons:
Personal menu' from https://addons.mozilla.org/en-US/firefox/addon/3895 (to remove and customize the toolbar buttons and menus)
All Glass Firefox Mod’ from here https://addons.mozilla.org/en-US/firefox/addon/12181 (For Vista and 7 users’ only. It will give glassy, aero look, like in IE7/8).