Knowledgebase:
When starting LockDown Browser, I receive a message instructing me to uninstall "Asus Virtual Camera"
Posted by Respondus Support

ASUS Virtual Camera is known to cause technical problems during exams that utilize Respondus Monitor (the webcam feature of LockDown Browser). As a result, students with the ASUS software installed will need to uninstall it before a LockDown Browser/Respondus Monitor session can continue.

To do this, you need to go to the Windows Control Panel > Programs > Uninstall a Program and select "Asus Virtual Camera."