You can use the tools provided by the specific HBA card vendor to get the WWN of an HBA card, for example, you can use SANSurfer for QLogic cards and HBAAnywhere for Emulex cards.
(There is another easy way to get the WWN of any HBA card vendor, just install NetApp Host Utilities and run the HBA Info in Start menu/All Programmes/NetApp/Windows Host Utilities/. Added at Jan. 13 2010 by xuming)
And if you bought the HP x86 PC server and have set up the server with the HP SmartStart or have installed HP System Tools on the server, there is a easy way to get the WWN number.
Just open the https://servername:2381 in your favourite web browser, follow the instructions below and you can get the WWN in easy way.