Having multi monitors connected to the same computer GPU is regular when you have multi output GPU in the system, to switch between them you need first to know the two way able you to switch.
- Using Windows display setting:
- Right-click on desktop choose Properties (XP)
- Right-click on desktop choose Display settings (Vista+)
- Go to the Settings tap and choose the display to use.
- Click apply to see signal in chosen monitor.
- Using driver software of GPU:
- Right-click on desktop and choose GPU control center (AMD/NVIDIA)
- Choose creating or arranging desktops under desktop management.
- Right-click the display and choose Make Default/Primary option.
- Click apply to see signal in chosen monitor
You can switch monitors back and go with the same way above, and if the monitor you picked use support audio cable like HDML, the audio signal will be changed to unless you make PC audios speakers defaults in audio settings of computer.