The only trusted source for drivers for any device is the manufacturer's own website: http://www.a4tech.com/driver.asp
However, there are no drivers for the PK-910H
webcam on the A4Tech website. They state that:
"No Driver Required for this Product
", which implies that the driver is built in to Windows.
My guess is they are referring to Windows Vista and/or Windows 7. It may therefore not be compatible with Windows 8.
if you wish to contact them by email to ask about Windows 8 support for the PK-910H
webcam, go here:http://www.a4tech.com/emailus.asp
Complete the enquiry form and click "Submit".