If that doesn't work, follow this guide -> http://mark.cdmaforums.com/ADB.htm
to install and configure ADB, and make sure you have the most up to date versions. Consider also installing the latest Google USB driver when doing so.
Also keep in mind, unfortunately there have been many with Windows 8/8.1 that have run into issues using ADB.
Please be sure to post back exactly what fixes/helps you so it can help others that might run into this issue.