Hello Cecile,
MAX will not be able to see a board that is not manufactured by National Instruments, so it's fine that it doesn't show up there. VISA, however, is a standard way of communicating and should allow you to connect LabVIEW to the HP hardware. VISA is a software layer that both HP and National Instruments can use. Our VISA Open, Read, and Write VI's will talk to the VISA layer to perform these operations. Both HP and National Instruments provide VISA layers, and there are ways to use each of them in your setup. We should probably start at the beginning and try to get a basic VISA session going to link to the hardware.
Check out these KB's for information on which version of VISA to load and how to configure it:
http://digital.ni.com/
public.nsf/websearch/0604CC2CF435C77086256B90005C651E?OpenDocument
http://digital.ni.com/public.nsf/websearch/E56D3D4866BE0A8A86256942006626F0?OpenDocument
Attached is a simple VISA VI (take a look at the block diagram as it will be helpful in your future VISA programming and troubleshooting) to test the VISA functionality. I tested this locally with my instrument, so it is set up for my National Instruments GPIB card. Your "VISA Resource Name" will undoubtedly be different from mine. See the above KB's for information about that.
I hope this helps you; if you need further assistance or clarification, please reply to me here.
Scott B.
Applications Engineering
National Instruments