Hope this helps
First try (you may have already) move mouse over the start bar, click left and hold while moving the mouse up and to the left.
When the start bar snaps to the left side of your screen release the mouse button.
Right click on the Configure the Start Button. Follow your instincts.
Second try using the right mouse button and select something in your right context menu that sound right, all right context menus are different. Therefore I could not tell what select.
Third try changing the screen sesolution in windows personalization (control panel) button.
OR
try changing the screen resolution by right clicking on an open area of your desktop.
Last sugg: I don't have win 8.1 as it is incompatible with my firewall SW.
Move mouse to bottom of yur screen as it is now and right click on an open area to the left of the cloct/task area and select the "Properties" link at the bottom of the context box, then either [TAB: Taskbar] check box "Use small taskbar buttons" or [TAB: Jump Lists] change the "Number of recent items to display in Jump Lists to something less that 12 in the box to the right. OR [TAB: Toolbars] clear all selections EXCEPT the DESKTOP toolbar. Then click "OK" And see if any of these help.
