Hi,
Maybe you have the same problem I just posted about: my HP printer (OfficeJet 8600 Pro) works absolutely FINE with 64bit apps, but appears INVISIBLE to 32bit apps.. of which there is still a great number around, not available in 64 bits. Are the apps you tried to print from 64 or 32 bits? I'd suggest Wordpad (which id 64 bits in Win7-64): if it prints fine, then you have the same problem as me.
Good luck!