Hi,
If you have a VI written (or saved) in 7.1, then you will not be able to open the VI in 7.0 (or any other previous version). However, in LabVIEW 7.1, you can save the VI as a 7.0 VI. To do this, refer to this
Knowledge Base
I hope this helps!
Travis H.
National Instruments
Travis H.
LabVIEW R&D
National Instruments