I'm setting up Mozilla Thunderbird on my computer and I'd like to hear from anyone who can recommend a program or add-on that will notify me when new emails come in. My Googling on the subject has left me thoroughly confused; I don't know whether I need to work this through Gmail, Thunderbird, or Windows.

I've just loaded Thunderbird 2.0.0.12.

I don't know if this is what you're looking for but when new mail arrives (with the program open/minimized) a small window pops up on the screen outlining the new messages. It "sticks" for maybe 10 : 15 seconds, then fades out.

Oh, you wouldn't believe it... I just opened T'bird to see which version I had and that message popped up.
Well, at least I know it works.
Thanks, Dan.

You're welcome.