Printer has power, but nothing works!

I got an HP Photosmart C3140 printer from my father. It didn't come with a cd, so I downloaded the drivers and all that from HP's website. I don't have any problems with installation. My problem is the printer. I plugged it in and it seemed fine. After I turned it on, now I can't get it to go off. Even if I unplug it, when I plug it back in it comes right back on. The light beside of check paper and check ink is on and won't go off. Also when I tried to check the ink, the thing that holds the cartridges won't move to the right so I can check them. It is like it has power to it, but nothing works. My computer won't recognize that it is hooked up, but it did when I first plugged it in earlier. I installed the stuff I downloaded from HP but couldn't get the computer to recognize the printer, so I uninstalled the drivers to try to start over from scratch. What can I do now?