Do you know that you can stretch and move your XP toolbar by clicking and dragging on one of the group of little bumpy dots along the bar? That is, one of those small columns of 7 dots (looking like golf ball dimples) which , in your image, appear in 3 places on the silver bar - to the far left, in the middle and to the far right next to the tray. Each section contained by the dots can be moved into another spot on the bar.
It may be that you just grabbed, moved or stretched one of the bar sections unknowingly.
By right-clicking on the bar you may further customize it...Or even lock it so it doesn't move.