If you are talking about the AddOns button that shows up on the character selection screen, this is not something that can be removed by using a FrameXML hack or otherwise. The only reason I can see for it not being there, would be if there are no addons in your Interface/AddOns directory (or they are not installed correctly.
Post back here with information on what is in your Interface folder. You should only have 1 folder, called AddOns, and inside that folder should be the addons that you installed...