If you cannot open an Excel file and see Excel cannot open the file because the file format or extension is not valid error, see this post.

Convert OpenOffice.org Calc spreadsheets into a Microsoft Excel file to take advantage of Excel's built-in tools. OpenOffice.org spreadsheets default to a .xsc file extension, which certain ...

If while opening an Excel file, you receive the “ Sorry, Excel can’t open two workbooks with the same name at the same time ” error message, the solutions provided in this article will help you.