Delete a security key from your security info. If you lose or no longer want to use a security key, you can delete the key from your security info.

如何激活预安装在新 Windows 10 计算机上的 Office 或使用新的产品密钥。

How to use the SUMPRODUCT function in Excel, one of Excel’s math and trig functions, using multiplication, addition, subtraction, and/or division to return the sum of the products of corresponding ranges or arrays.

Insert a text watermark to the pages of your documents.

Learn how to use and customize ActiveX controls and filtering in Internet Explorer.

Use data validation rules to control the type of data or the values that users enter into a cell. One example of validation is a drop-down list (also called a drop-down box or drop-down menu). Watch more in this video.

Get answers to all of your Microsoft Word questions. Find Word help, how-to articles, training videos, tutorials, and more.

Learn how to free up space for Windows update including deleting nonessential files, using an external hard drive, and updating your hard drive.

Learn how to activate Windows using a product key or digital license, check your activation status, and link your Microsoft account.

In new Outlook you can grant anyone within your organization editor or delegate access to your calendar. What's the difference between edit permissions and delegate permissions?