Do not attempt to change your Live ID. It will not help, and it may confuse things.
You will need to remember the credentials in effect when you were last in that Money file.
Disconnect from the Internet. If using Money Plus, change the date on your computer to a date in January 2011, such as 2011 Jan 15. Start Money, and log in offline with the credentials in effect when you were last in that Money file. (the changing
of the date may not be needed, but it won't hurt.) Remove your LiveID. Do not attempt to change your LiveID. To remove the Live ID, go to File-PasswordManager, and choose to remove your LiveID.
If you do not remember the credentials in effect when you were last in that Money file, no. Try hard to remember. Look thru the papers or files where you recorded such things to see if you made a note that you can find. Write down what you think can
remember, and maybe that list will help you later when you try the various permutations.