Sorry, but the first time you open them in LV 6.1 your old VIs will get converted to the new format. The good news is that for the most part basic functionality has changed very little so there should be a minimum of compatability problems. Still you will need to test them--how big that job is depends to a large extent on how modular and reusable the V4 code is.
The biggest problem I have had in the past with this type of project is to supress the urge to "cleanup" old code by taking advantage of the advanced capabilities of later versions.
Mike...
