Deskjet 2050 - device not recognised USB problems

My tech savvy girlfriend got a bit too excited and plugged in our brand new deskjet 2050 printer to the USB before the software had been installed. Now the printer is not recognised - "USB Device Not Recognised" message appears. I have tried uninstalling the USB drivers, taking battery out and leaving overnight - no luck. At one point there was a yellow exclamation point and "Serial" entry under "Non Plug and Play Devices" in Device Manager - I uninstalled it, along with the HP Driver and Software. Reinstalled the HP Driver - and the printer worked - until I turned it off and back on again. I've tried everything suggested on all forums and in the HP Support Documents, but nothing works. The printer works fine on our friend's computer. I can't believe that there is no way to fix this problem. Do I have to sell a brand new printer? Any help would be gratefully appreciated.