Help, Taskbar has changed theme and won't change back?

Help! My computer is a Window XP and for the first 2 and 1/2 years the taskbar is blue with a green start button. But Today when i open the computer the taskbar changes to the old style theme like for the window 95. How do i change it back? I tried changing it but it won't work! WHAt do i do???!!Help, Taskbar has changed theme and won't change back?
click start.

click preferences

click taskbar and startup menu

change to one you want.

also you can go to

start

conrtol panel

themes

windows xp theme