Because the driver is unsigned and potentially targeted by antivirus (false positives), official sources no longer exist. However, you can find clean copies on:
Hosts version 1.2.0.0 specifically for Windows 7 64-bit. dvr card techwell tw6802b driver for win 7 64 bit hot
Occasionally required for transport stream processing depending on the specific card model. Where to Download Because the driver is unsigned and potentially targeted