One of our accountants, newly introduced to Office2007 is opening a workbook
and finding 3 instances in her Taskbar. Each one is with a different format.
Presumably, each one represents a different compatible format for each
version of office?

The title bar indicates (Compatibility mode). However, she states that she
has opened other workbooks in (Compatibility mode) and they display 1
instance.

Can someone please point me to an explanation on this?

Thanks