The way menus are opened depends on the SystemParameters.MenuDropAlignment property. This is usually set to align to the right if you have a tablet computer configured for right-handed people. The setting can be changed for the computer in Control Panel -> Tablet PC Settings -> Specify which hand you write with. If you don't have Tablet PC Settings in your control panel you can try running shell:::{80F3F1D5-FECA-45F3-BC32-752C152E456E}. This class fixes this setting so popups are dropped-down with a usual orientation.