O cabo de áudio virtual pode funcionar se você desabilitar a verificação de assinatura do driver, conforme explicado no arquivo de ajuda incluído no ZIP:
There are two ways to successfully
load VAC driver under 64-bit Vista and
2008 Server systems:
At early boot time, press F8 and
select "Disable driver signature
enforcement". In this mode, Windows
will not check driver signatures
during current session. But if you
reboot Windows, you should press F8
and disable signature enforcement
again. So you need to make selection
at every boot.
Enable Windows
test-signing mode by one-time issuing
"bcdedit /set testsigning on" command
from a command prompt (under
Administrator account). This
permanently allows Windows to load
drivers signed by test certificates.
After issuing bcdedit command, reboot
Windows. 64-bit VAC driver module is
signed by a test certificate named
"Eugene Muzychenko (Test)" so it will
be successfully loaded in the
test-signing mode.
Eles explicam para o Vista e o Win2008 de 64 bits, mas também são válidos para o Windows 7.