A scroll bar helps you scroll down a web page or a window in Windows Explorer. For various reasons, your scroll bar may disappear from the screen. Chances are that the scroll bar is probably stuck or has reduced its width to its minimum. This process will help you get the scroll bar back to the screen in its original form.
Restart your computer. Sometimes, a simple restart can bring back the scroll bar to its original form.
Right-click anywhere on your desktop. Click on "Properties" if you are using Windows XP. Select "Personalize" if you use Windows Vista or Windows 7 and click on "Windows Color and Appearance." Then click on "Open classic appearance properties for more colour options."
Click on the "Advanced" button.
Click on the "Item" drop-down menu. Select "Scroll bar."
Change the width by entering "17" under the "Size" category. 17 is the default scroll bar width for Windows operating systems.
Click on "OK" and select "Apply" to end task.