Unless you're using a Microsoft account that already has a picture associated with it, Microsoft set your profile picture to the default user picture for Windows---a generic silhouette of a person. To change the picture, hit Start, click your account picture on the left side, and then click the "Change Account Settings" command.

Local account profile pictures are controlled by the Settings app. Launch Settings from the Start menu and click the “Accounts” section. You’ll arrive at the “Your info” page. Your current photo will be prominently displayed. Click the “Browse for one” button below to choose a new image for your account.

Select Start > Settings > Accounts > Your info. Under Adjust your photo, select Choose a file > Browse files to select an existing photo. Or, if your device has a camera, select Take a photo > Open camera and take a new photo. Note: Windows remembers the last three pictures you’ve used.