Tom,
To perform overlapping FFT in LabVIEW you'll have to extract the different overlapping time segments your self. There are 2 different options, either extracting the time segments one by one from your overall signal, or by passing the needed overlap section using a shift register inside an additional for-next loop.
If your overall signal is not too big, I'll recommend you to use the first technique, but if your signal is very long or runs continuously, you'll have to use the second technique.
The attached example shows how overlap FFT works on a relative short transient. The VI is explained on the front panel. (LabVIEW 6i or higher required)
Alain
