If you are asked for a keychain password after you log in to a Mac.
The keychain password is the same as the login password by default, and is supplied when you log in. If you change the login password through the password reset method they don't match any more, which is what causes the request for the keychain password.
You can delete the old keychain and you will be asked to create a new one which you can set the password for. If you make it the same as the login password, the prompt for the password should go away.
Important Note: You will lose all the passwords stored in the keychain, but if you don't know the keychain password they are inaccessible anyway.
From the desktop/Finder, click the Go menu. If you see "Library", choose it. If you don't, hold down option key and it should appear. In the folder that appears, delete the Keychains folder. If you can't delete the folder, delete its contents. Logout and login again, or restart. You should be asked to create a new keychain. Set the password for this to the same as the login password.
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