If your Excel files are opening in Notepad on Windows PC, here's how you can reset the settings to make .xls, .xlsx, etc files open in Excel.

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.

Expand your file-protection options via Microsoft Office 2007's Trust Center The most recent version of the popular Office applications centralize security options and add a few new wrinkles.

With that, the cached Excel files are wiped away easy. While you're in the Cache Settings, you can also use the options there to control how long Excel holds onto cached files for.

To display specific values in a PivotTable in Microsoft Excel, use one of the many built-in filters, such as Top 10.