Audio driver installation changes Windows default devices. How to

I am trying to install virtual audio cable drivers. However on some systems
after installation the Windows default audio devices are replaced by the
virtual devices. We have already added following to the registry:

[HKEY_LOCAL_MACHINE\SYSTEM\CurrentControlSet\Servic es\VirtualCable]
"Start"=dword:00000001

but its still changing the default driver on about 30% of the systems.

Any idea how to fix this?

Thanks!

Dick Schiferli