Hi tanu,
It is possible to use the VISA Driver Development Wizard to create a driver for your USB device, provided you have all the necessary information about the device such as vendor ID, product ID, and communication protocol. Here are a KnowledgeBase entry and a Tutorial that should help you get started:
http://digital.ni.com/public.nsf/websearch/E3A2C4FE42D7ED0D86256DB7005C65C9?OpenDocument
http://zone.ni.com/devzone/conceptd.nsf/webmain/6792bab18242082786256dd7006b6416
If all you are wanting to do is write data to the USB drive, then it might be easier to let the OS use it's own driver and just accesses the mounted drive with LabVIEW.
