New Thunderbird crashes on opening

I can open my new Portable Thunderbird - but it more or less immediately crashes.

This is mainly why:

it took my existing email account info. and rather than linking to xxx@blueyonder.co.uk directly, linked to it via my virgin/gmail account. Virginmedia supplies my blueyonder account, and holds all my email on gmail, (accessible via a browser), as well as supplying it to the email prog. on my computer.

That meant Thunderbird immediately downloaded *40,000* old emails from gmail, and not just the latest handful.

I deleted nearly all of them, but the program still seems to be screwed - perhaps because it hasn't totally deleted them.

How do I get out of this mess? Since Thunderbird seems to be a truly portable app, I can't just uninstall it from the system and start again.

Thx for any help.