Updated driver file download path. Seems that unable to download from A4Tech site by now. Here is the original link to A4Tech PK 635 http://www.a4tech.com/en/driver/A4%20pc%20cameraH.zip
A4Tech PK 635 Driver
Download IC50C Webcam Driver
Old link to the driver file http://www.mic-innovations.com/driver.sdrv?id=100017 is not working. [20080821] New link updated.