Try pressing CTRL+ALT+Up Arrow.
Or
Check your adapter properties for screen rotation settings.
Right click the Desktop, click Properties > Advanced tab.

Signature
Brian A.
Conflicts start where information lacks.
http://www.dts-l.org/goodpost.htm
> After booting up with landscape orientation, the desktop
> appears rotated 90 degrees. Other than turning the
> monitor on its side, how can I correct the problem?