It's a failure of Thunderbird to register properly with the OS.
Try uninstalling and reinstalling Thunderbird.

--
Gary VanderMolen, MS-MVP (WLMail)


"craighanoch" <craighanoch@discussions.microsoft.com> wrote in message news:F83A8896-1BBA-4FEF-B869-A6823B4A60E3@microsoft.com...
> After installing Office 2003 on a Dell 1330 with Vista Home Premium, the
> default mail tool changed, of course, from Thunderbird to Outlook. I
> uninstalled Outlook, and the default email tool changed to Windows Mail.
>
> I have tried using the Default Programs control panel and other means to
> change the default email tool back to Thunderbird, to no avail. Each time it
> starts it asks me whether I want Thunderbird to be the default. Each time I
> click yes, but the setting doesn't hold.
>
> I have gone through all the usual steps to define Thunderbird as the
> default. In Windows Mail, the option to change it so that it is not the
> default is mysteriously grayed out.
>
> Any suggestions how to get around this? Windows Mail seems more like a virus
> to me than a legitimate piece of software. It doesn't even show up in the
> list of Windows services, so I can't even turn it off!
>
> What's so weird about this is that it all worked fine until I installed
> Office 2003 ... now, I can't change the default mail tool.
>
> And, yes, I am signed in as admin.
>
> Thanks,
> Craig
>