C.,
a LabVIEW string is more like a Pascal string, rather than a C string.
To write binary data you should create a string constant or control, right-click on it and choose "'\' Codes Display" or "Hex Display". Now you can enter a null Byte as '\00' or '00' (without the quotes, of course), depending on what type of display mode you have chosen. The first mode ist easier to combine with normal printabel text, whereas the latter is better for binary strings.
NI Spy was installed here in C:\Program Files\National Instruments\NI Spy\NISpy.exe. It might be a component with higher level versions of LabVIEW, not with the base version.
But if you create probes you could as well debug your app without NISpy.
HTH and
Greetings from Germany!
--
Uwe