We have a vendor-provided corporate application that is integrated
into our Offce 2003 suite (database queries behind the scenes, etc.).
The part of the application that I see is a toolbar in Excel (all
machines are WinXP). Unfortunately, their program is poorly written,
and does things like hide commandbuttons in other workbooks, etc.

When I go into Excel View/Toolbars and click to suppress viewing the
toolbar, it goes away...but the next time Excel is opened, the
toolbar comes back (is automatically visible again). Of course, the
presence of the toolbar itself isn't likely to cause the
commandbuttons in other workbooks to dissapear, but I figure if I can
find the code that is auto-showing the toolbar, I might find the rest
of the code as well.
I didn't find any add-ins, nor any files in any startup folders (at
least anywhere I could think of).

So, if you wanted to tick off your customers by figuring out a way to
make a toolbar visible every time Excel starts, how would you do it?
I'm asking because I want to use your ideas to work backwards and
figure out where their code is, so I can figure out a workaround. It
is possible that they might be using some .NET code somewhere that
puts the toolbar back anytime Excel opens, but I wouldn't even know
where to look for something like that if the code isn't in Excel
itself. There might also be other directories where some sort of very
hidden add-in might be located that I don't know about, so any ideas
would be greatly appreciated.
Many thanks,
Keith

Is there a hidden workbook that opens every time Excel opens? If you click
Window | Unhide (if Unhide is not greyed out) does the name of a hidden
workbook appear? If so, this workbook is set to open each time Excel opens,
via the setting at:

Tools | Options | General | At startup, open all files in: ...

If you find such a workbook, check for code in its Workbook_Open event by
double-clicking on its ThisWorkbook item in the VB explorer window. This is
probably where your rogue toolbar is created and loaded.