The licensing of Virtual CD must be done with administrative rights. Please check whether the registry key

• HKEY_LOCAL_MACHINE\SYSTEM\CurrentControlSet\Services\obvious.ini  (Virtual CD v6)
• HKEY_LOCAL_MACHINE\SYSTEM\CurrentControlSet\Services\vdrv7000.ini  (Virtual CD v7)
• HKEY_LOCAL_MACHINE\SYSTEM\CurrentControlSet\Services\vdrv8000.ini  (Virtual CD v8)
• HKEY_LOCAL_MACHINE\SYSTEM\CurrentControlSet\Services\vdrv9000.ini  (Virtual CD v9)

exists and whether the group of administrators has full access to it.

HINT: Please be note that this error may occur independent of the access rigts if you try to register Virual CD up to version 8 under Windows Vista. Virtual CD fully supports Windows Vista as of version 9.
Please also see:

• Virtual CD and Microsoft Windows Vista
• Which Virtual CD Version supports which operating system?