Just signed up for what? Thunderbird is email client software that you install on your computer. It connects to the email servers that you enter account info for. In order to enter that account info you need the username and password. You entered the info. You should know what account you entered.

Here is what I get when I launch Thunderbird application. See attached...and this isn't my stuff...it's from someone I do know...but shouldn't be on my computerer...Bevlesly@gmail.com

I entered my email address and my own password...not the one that shows up....I don't even know the password of this person's email address...this is some kind of weird crossover from someone else's account....how can I get this fixed? I do know what I entered...and it wasn't this person's email address...!!!

Is this a computer that the other person used at one time? If so they did not delete their Profile info and Thunderbird picked it up when you installed it. This is not rocket science or weird crossover. The info has to be placed into Thunderbird to receive the email. When you look at the account listing do you see this other account listed along with yours? Just remove the account and get on with it. Tools-Account Settings Select the old account At the bottom of the account list is Account Actions-Remove Account