Mix up of buttons in Excel Add-In ribbon - how to delete buttons?

Hi,

a few years ago, I wrote an add-in for Excel 2003. Later I had someone convert it for 2010. All was well, until I recently opened an old xls that contains code to load a command bar. All those old buttons now made a mess of my add-in ribbon.
How can that be fixed? I understand that there should be an xml somewhere, where buttons are defined. But which file is it?

Thank you!

Thank you! That was simple. Took me more than an hour of searching and browsing forums etc.
I was not able to delete individual buttons, though, but only complete command bars. With a warning that this cannot be undone. I was afraid that it would remove *everything* including the buttons that I wanted to keep.

Still, would you know how to find the xml that defines my add-in buttons? It must be an xml. I know how to create new ones with Custom UI. But I don't know how to find old ones ...

Thanks again. That file contains code to show the AddIn tab, but not the actual buttons. I spent more time trying to find the button definitions, to no avail.