sounds like an auto hide issue
1. Move your mouse cursor right to the bottom of the screen until the taskbar appears.
2. Right-click on the taskbar and select "Properties" from the context menu. The "Taskbar and Start menu Properties" window should open.
3. With the "Taskbar" tab open, UNCHECK the box labelled "Auto-hide the taskbar".
4. Make sure there is a check in the box labelled "Keep the taskbar on top of other windows".
5. Click "OK" to save the changes and exit the properties window.