Heres a tutorial to make your Firefox 3 look like Windows Vista Explorer.

First you'll need an add on called (Glasser) for Firefox 3 only!

You can get it from here [link]

This will give Firefox an Aero Glass frame (Windows Aero only Vista Basic not supported.)

Second you'll need an add on called Stylish.

You can get it here [link]

This allows you to easily edit Firefox's chrome.

And now you'll need to add a Userstyle to Stylish to give it the Windows Explorer look.

Here is one i've modified [link]

Heres one i modified to have a Red Bookmark toolbar.

[link]

i will add more colors soon

To install just click on stylish go to Write Style > Blank Style. Then copy and paste the contents of the FF3_VistaExplorerStyle.php file into the body, and type in a short description. then click save.

And you're basically done.

You can also use a few other add ons to even further integrate it with Vista

Fission (joins the loading bar with the URL bar)
Personal Menu (Hides the menu bar and replaces it compact buttons)
Tab Preview (Gives the tabs a kind of Vista style preview on mouse over)

You can get all of these from the Mozilla add on site.