These are multiple windows to the same workbook.

They happen when you choose Window/New Window

You can prevent this by not choosing Window/New Window

You can get rid of the extra windows by clicking the close box on all
but one.

In article ,
wilmadeit wrote:

When I open this file I get two worksheets that open and under "Window" I'll
have book.xls:1 and book.xls:2.
What are these? How does this happen? How can I prevent this?