For
some systems (mainly notebooks) the part number is contained in the Model property of the Win32_ComputerSystem class. The number is preceded by the product name:
HP Compaq 6710b (GR680ET#ABH)
HP Compaq nx8220 (PY516ET#ABH)
HP dx2000 MT(PE205ET)
Unfortunately, none of the servers and only part of the desktop systems I've seen show any part numbers. The SKU and PartNumber properties of (for example) Win32_SystemEnclosure have no values assigned. Using the HP Client Management Interface (
http://h20331.www2.hp.com/Hpsub/cache/284014-0-0-225-121.html) doesn't help.
According to the last post on
http://episteme.arstechnica.com/eve/forums/a/tpc/f/12009443/m/845004416931 HP's Systems Insight Manager can extract the part numbers of ProLiant servers - I haven't tried this myself, though.