If the device is not showing up under system profiler then i believe the the computer is not recognising it
Try using a diff cable or powercyle ur computer once.Hope u have connected printer directly to computer not thru an USB hub.Also u can try doing a PRAM reset
and i believe u have downloaded this driver:
http://h10025.www1.hp.com/ewfrf/wc/s...os=219&lang=en
Further u can try getting help from this link
http://support.apple.com/kb/HT1791
Good Luck