Installing TBS6903 W7 64 - Unsigned Driver problem

This is driving be nuts. I've searched the usual places for help but can not install the v1.0.0.5 Windows drivers for a TBS6903 on a Win7 64 bit SP1 OS. The PC is firewalled from the internet but I even tried disabling that (it is on an intranet). This is a new installation of the card on the PC that can also have the TBS6983 (which works). I've tried disabling signing enforcement by several methods including
That even shows the watermark warning it's...

Installing TBS6903 W7 64 - Unsigned Driver problem