Thanks Artik!
You are right, i looked for it and found out that it is part of the "Application.COMAddIns" collection and called "Microsoft Power Pivot for Excel".
I spent couple of hours googling and researching, but I had no success of finding a way to do it - is it possible at all to disable the add-in in the XML? the same way we can disable a home or data tab with its idMSO?
Thanks!