How to edit Password Manager in Win 7/IE11/Thunderbird

Dumbfounded! I tried to find the location of the password manager within Windows 7 - 64 (control panel), IE11 Tools and Thunderbird Tools, but I have not found anything there. Where can I find this password manager? Whenever, I open Thunderbird, I get prompted to enter the PW for each of the email accounts. There is also an option to allow a "password manager" to remember the password. I have never installed a password manager, so I don't know if it is part of TB, Win7 or IE11. That's my first dumb question.
The worst part of this is that I don't intend to use ever a password manager. I don't trust them, in fact I don't trust any web based data storage system. Companies can go belly up and/or bought out and customer data gets lost or even worse merged with other companies systems that don't match, whereby your own data gets mixed with somebody else's data (different ISP but same screen name), which can cause great havoc and despair. (example: AOL merge with CompuServe and Netscape). Enough of that.

My problem right now is that one of my email accounts in Thunderbird suddenly opens up without asking for a PW. I have not consciously ever opted for a password manager to be used. I must have accidently clicked on that option and now this account is no longer PW protected.

Thus, after finding the culprit password manager, my second dumb question is how to remove the password from it, if that is possible (not sure about that?). Could someone help me with that? I would be very thankful.
Derek

Thunderbird:
This article is about changing passwords...
https://kb.wisc.edu/page.php?id=19006
...but you can use the info to remove/delete passwords too.

Windows 7:
Click on Start
Search for Credential Manager

IE11:
Open IE.
Click on the gear in the upper right corner.
Select Internet options.
In the Internet Options window, click on the button named Delete...
Read