As you can see, lots of border and toolbar transparency. You basically have two options at your disposal to get rid of the Aero theme and transparency that comes with it: Install a different theme.

Ignore Aero

Ignore Aero is a theme for the Thunderbird email client that disables some, but not all, of the Aero effects. The title bar and borders still use transparency, while the other toolbars do not.

The extension is not an ideal solution for users who want to get rid of Aero completely, as it reduces the Aero effects only in the email client. You can download the Ignore Aero add-on for Thunderbird from the Mozilla Thunderbird Extension repository.

Alternative themes that pretty much have the same effect are NoGlass or Classic Reloaded.

Compatibility Workaround

You can run Thunderbird in compatibility mode to disable Aero automatically and only for that program and no others running on the system. For that you need to right-click the Thunderbird shortcut that you click on when you start the email program and select Properties from the context menu. Switch to the Compatibility tab in the Thunderbird Properties window.

Enable “Run this program in compatibility mode for:” and select Windows XP (Service Pack 3) from the options.

Running Thunderbird in compatibility mode has the same effect as installing one of the themes mentioned earlier in this article. The title bar and borders remain transparent, the other toolbars turn solid.

Disable Aero transparency

If you dislike the Aero transparency, you can disable it in Windows 7 by right-clicking on your desktop and selecting Personalize from the options. You then need to click on Window Color at the bottom of the Personalization window. Here you can uncheck “Enable Transparency” to disable it completely or use the color intensity slider to modify it.

Inspiration for this post taken from Ask VG.

The email client has to be closed and opened again before the new theme becomes visible. It also has to be activated from the themes tab in the add-ons menu before it becomes visible. The easiest way to accomplish the whole process is to install the theme, switch to the theme tab, activate the new theme and restart the browser then.

Many of the themes for Thunderbird at the official Mozilla Thunderbird website do not work with the latest version of Thunderbird which is surprising to say the least. It is probably possible to force compatibility but that has not been tested. All themes listed in this article are working with the latest version of Thunderbird which is currently 2.0.16. They probably will also work with Thunderbird 3.

ACE CuteBird (Graphite)

Azerty ‘mail

Walnut

Modern Modoki

CrossOver

Simple Green

Noia 2.0

PitchDark

Additional themes are available at the themes repository at Mozilla.com.