I can't load it into 5.1 or 6 because you didn't attach the .llb for the whole program. There are VIs missing. It appears that it is calling some acquisition VIs that are not part of LabVIEW 5. If you are using non-NI hardware, the problem may be in the driver for it. Either it's not installed on your system, it can't be found by LabVIEW 6, or the driver has some VIs without a diagram. If there is no diagram, you won't be able to convert from 5 to 6. If you want to attach the main with all subVIs, go to save with options and choose Development Distribution.