Sorry I only know how to do that using Add/Remove Programs. In there you can either Modify, Remove or Repair. I have had trouble with NI-MAX once and a Repair was good enough to sort the issue. That issue was something complete different though.
Can you not just close both instances of NI-MAX down and only open one up? Try and start NI-MAX from within Labview by going to the menu Tools -> Measurement and Automation Explorer and see if that helps.
Its pretty likely that you only have one install for NI-MAX under National Instruments. This might be different if you have installed Labview in two seperate places on your hard disk.
