Your Windows taskbar could have disappeared due to one of several reasons. It may simply be hidden. It could have been moved or minimized. Or the Windows "explorer.exe" file could have stopped running.
Hidden
One of the first things you should check if your Windows taskbar keeps disappearing is your taskbar properties. When "Auto-hide" is selected in the taskbar properties, your taskbar is only revealed when you mouse-over the area where it's supposed to be located. Uncheck "Auto-hide" to stop it from disappearing.
Video of the Day
Video of the Day
Minimized or Relocated
It's possible that your taskbar may have been reduce to a size, or moved to a location that makes it difficult to see. Mouse-over the entire parameter of your screen, beginning with the bottom edge of the screen, if a vertical double-headed arrow appears, it's an indication that your mouse is hovering over your taskbar's border. To resize or relocate the taskbar so that it's clearly visible, when the vertical double-headed arrow appears, click and drag it to resize or reposition your taskbar.
Explorer.exe Glitch
The "explorer.exe" program is responsible for displaying your taskbar. If it freezes or stops running, your taskbar will disappear. The "explorer.exe" can be restarted from Windows Task Manager.
Restart Explorer.exe
Open the Task Manager by pressing "Ctrl," "Alt" and "Delete." Go to the "Processes" tab. Locate and right-click on "explorer.exe," and then select "End Process" from the shortcut menu. Open the Task Manager "File" menu and select "New Task (Run...)" Type "explorer" and click "OK."
Virus
If the problem does seem to be the result of an "explorer.exe" glitch and it's a frequently recurring problem, you should scan your computer for viruses and spyware. Your computer may be infected with something that's interfering with the proper functioning of this file.