A mobile device having a user interface supporting multiple windows is disclosed. The user interface is suitable for use in any device having a handheld form factor, such as a mobile phone or mobile Internet device. The user interface includes two windows that are displayed on the mobile device's screen. The mobile device may be configured to switch between a single window mode and a dual window mode. The device may also be configured to launch applications in either mode. It may be configured to switch between modes automatically or in response to a user command. The windows may also be re-oriented in response to a change in the device's orientation or to a user's command.