Thunderbird screwed after attempted update.

Hi! I'm hoping you can help me! I use Thunderbird, and have for many years, and I love it. My computer is on its last legs, and I'm trying to save up for a new one, but, yesterday I did something possibly stupid... (yeah, I know, you NEVER get people asking for help who've done stupid things, so this will be unusual... lol). Anyway... I turned my computer on and got a popup saying that my Thunderbird needs an update and it's been a while since I updated, so I hit OK on the update... Well, my arsehole of a computer chose that exact minute to shit itself and die. When I tried restarting it, my Thunderbird no longer works. Now I have a popup with a big red X that says "The installation seems to be corrupt. Please check your hardware and disk setup and/or re-install." Can you help me? I desperately need to check my email and have one I need to send. I don't know what to do. I've also got YEARS worth of emails sitting in the system, so I can't risk losing them, either. Please help. L.