You may have your Windows Taskbar "stretched" up too high
and it's masking the bottom of the Excel window. Move the
mouse over the top edge until you get a vertical double-
ended arrow, left-click, and drag down.
It is also possible to drag the horizontal scroll bar over the tabs, hiding
them. Click the the left of the arrow at the left of the horizonatal scroll
bar; if you get a two-headed arrow, drag it back to the right.
