Hey Arabi, You need to tell us more about the controller you are using. Is this a custom device or something that has been developed by a company?If it's a common device, you probably can find the relating driver in <a href="http://www.ni.com/devzone/idnet/" target="_blank">Instrument Driver Network</a>. The instrument drivers have to be placed within the \National Instruments\LabVIEW X.X\instr.lib\ directory once they are downloaded and unzipped. Then close and open LabVIEW. Open the Functions Palette and navigate to Instrument I/O » Instrument Drivers to view the instrument driver that was installed. Also do refer to <a href="http://zone.ni.com/devzone/cda/tut/p/id/2804" target="_blank">How to Use an Instrument Driver in LabVIEW Tutorial</a>. Have you managed to get Windows to communicate with the controller?The first step would probably be to install the drivers that come with the controller. What do you mean by "already designed to interface with the circuit"?Are you using VISA commands to interface with the circuit? Please be a bit more detailed as to what you mean by installing driver or at least what kind of driver you are talking about.