Hi Sean. I am an Excel user like you.
Here are a couple of things to try. Sometimes a window can somehow be re-sized to a very small pinpoint that although it is on the screen you can't see it or if you can, you can't do anything with it.
- Put your mouse over the label in the task bar. A small preview window should open up. Move your mouse over the preview window and right click. You will get a menu that includes Maximize. Click on that and the Excel window should open to full screen.
- If you can open a different Excel file that you can see, while both workbooks show to be open, on the View ribbon click on Arrange All and select Cascade and OK. This will reset the size for the Restore Down of both windows to a larger size. In addition, if #1 works to open the window to full screen, do this also to reset the Restore Down so it doesn't go back to the micro size it started on.