If this is under Windows, just go to the control panel and click on add/remove programs (or similar). This is the same as with any other software.
Look for a entries that start with "NI ...", then uninstall them. Depending on what is installed, you might also have a universal entry called "National Instrument Software". Click "modify" and you'll get a list of all NI software and you can select what to modify or unistall.
Have you already tried this, but have encountered problems?