Dear Martin,
Many instrument drivers can be downloaded from NI by going to http://www.ni.com/devzone/idnet/ and selecting "Search for a Driver." In this case, the driver for the VM3608A is not available on the NI web site. This driver is available from VXI Technologies, the manufacturer of the VM3608A. You can download the driver by going to http://www.vxitech.com/download.asp and selecting the appropriate instrument driver.
Regards,
David Shatila
Applications Engineer
National Instruments
www.ni.com/support