Here's something Internet Explorer 7.0 can't do!
Head on over to the Firefox Add-ons page and pick yourself out a new theme for your Firefox browser.
I personally like Noia 2.0 (eXtreme) and you may find something you like as well.
Once you download it, Go to Tools, Add-ons and then click the Theme Tab. You can then click on "Use Theme" and you are good to go!