1. Type about:config in the address bar and press Enter.
2. Press the big button to bypass the warning.
3. In the search box, paste browser.tabs.onTop
4. In the search results, double-click browser.tabs.onTop to set its value to false.

Note: If you're using either Windows 7 or Vista with an Aero Windows theme, performing the above will make a large part of the Firefox window glassy. If you find this unpleasant, the simplest thing to do is to install a persona.

• https://addons.mozilla.org/firefox/personas/solid

Thank you for the response Gingerbread Man, unfortunately the tabs have now completely disappeared.

You can check for problems with the localstore.rdf file.

• http://kb.mozillazine.org/Corrupt_localstore.rdf

Thanks but how can anything be corrupt after a fresh install? This is getting too complicated.

The localstore.rdf file stores your toolbar customizations (button order and such). Bad extensions are usually the reason it gets corrupted. In case of problems, you can restore toolbars to their defaults as follows:

1. Right-click an empty area of the navigation toolbar or tab bar and choose Customize.
2. In the window that opens, click the Restore Default Set button.
3. Click the Done button afterwards.

If for whatever reason that's not enough, you can manually delete the aforementioned file:

1. Type about:support in the address bar and press Enter.
2. Click the Show Folder button.
3. Exit Firefox.
4. In the Windows Explorer window that opened earlier, delete the localstore.rdf file.