Project Explorer Strangeness

I'm wondering: at times, after closing and re-opening various files, my Project Explorer window shows a project name more than once. After it does this, I'm unsure which project refers to the file I actually have open.

Is there any way to prevent this from happening or is there any way to be sure I'm in the right project in the IDE?

Thank you for your help.

I have never seen this occur in Excel. But a quick and dirty way to check is to go to the workbook you want to work on and add a new worksheet. Then go back to the Project Explorer to see which version has the additional worksheet.