Actually the 776899-01 ships with no drivers. The GPIB-232CT-A User Manual includes a section on commands which can be used to control the device over the serial port. This allows the unit to be controlled from any device with a RS-232 port, eliminating the dependency on driver software.
The 776900-01 includes DOS/Windows drivers, which will allow it to look like a standard NI GPIB interface on older Windows platforms. The
GPIB Driver Versions page will elaborate on which versions of Windows have driver support for this device.
Let us know if you have any other questions!
Jason S.
GPIB & Serial
National Instruments