Windows 8 and Windows 10:
No drivers are needed, support is already built into the operating system. Just plug in and reboot.
Windows 7, Vista, XP, Server 2008 and R2 (32 and 64-bit)
Plugable PCI-e cards purchased 10/16/2012 and after are µPD720202 based and require the 22.214.171.124 driver package. These units will be presented in device manager with the VID/PID pictured here:
Download and install (Installer version 126.96.36.199; Build date: September 28, 2012; Release Notes