Are these two accounts both members of the local administrator's group?
Are either or both of these accounts linked to your Microsoft Live ID?
And the answer to the other two questions?
The auto-login can be halted using the run command and typing
netplwiz
hit enter or click ok
select the bell south account and make sure that the box at the top is check "Users must enter a user name and password to use this computer"
You may have to toggle it off and on again by using the apply button.
And if you wish then you can switch the other account to auto-login using the same tool.
Home edition is a little bit more clumsy but you should be able to go here
Control Panel\All Control Panel Items\User Accounts\Manage Accounts
And select the account you would like to get rid of the one you do not want to use anymore.
I caution you against or at least about doing this without first making sure that you are absolutely certain that the remaining account is a member of the local administrator's group.
AND
That the profile folder, no longer contains anything that you consider important.....
C:\Users\OldAccountName\ (documents, picture, music, favorites, etc., etc.,)
AND
If one and not the other is currently linked in any fashion to your Microsoft Live ID, that may be worth some consideration.
