The key here is that all of them are showing up in LabVIEW 7.0. FieldPoint Explorer only installs one set of FieldPoint VI's, although it is possible to run custom installs in order to provide support for different LabVIEW versions (by default only the most recent installation is supported). Since you are still seeing the VI's, albeit with some of them having question marks, then what has most likely happened is that you have saved several of the FieldPoint VI's into LabVIEW 7 which is why LabVIEW 5 can not recognize them. If you have another machine that has LabVIEW 5 on it, you probably want to copy the ..\vi.lib\fieldpoint folder from that machine to the vi.lib\fieldpoint folder of the LabVIEW 5 directory.
Regards,
Aaron
LabVIEW Champion, CLA, CPI