Get 2tb.
Clone your existing c: partition to it. You should get right where you left of with space doubled. You might need to "extend" drive. Or format blank partition and use it as second drive. (each partition - separate drive) Label old 1tb with date, keep it as backup. I've done this a few times.

NI stuff, if you decide to move. Default location:
C: > Users > Public > Documents

Select instruments you want to move, CUT and paste where you want them. Launch Native Access. Refresh (there is a button there). Your moved instruments icons (in native access) will have exclamation marks with drop down menu with couple of options. One will say something like "relocate " just point to the place where you moved these instruments.

P.S. I made 2 partitions on my drive. (became 2 drives). One is active, C: Windows, programs etc and one is just for NI and other libraries.