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.

How to Open a Zip File in Excel 2007. A ZIP file usually contains several other files that have been compressed to a smaller size and bundled into a single package with a .zip filename extension.

If Microsoft Excel opens a Blank screen when you open an existing file, then you can stop Excel from opening a Blank workbook or sheet.

OpenOffice.org spreadsheets default to a .xsc file extension, which certain versions of Excel can't read. Microsoft Excel offers a pre-2007 file extension of .xls and a post-2007 file extension of ...