On my hp psc 1315

On my hp psc 1315 all in one, the check print cartridge light is flashing. I followed the diagram and took out the little box inside on the left (the only side there was one) and put it back in on the right side to see if that would help. Now the light still flashes and I cannot seem to remove the box from the right side. Any suggestions? I don't have a manual or anything other than the printer... it was a gift from a friend who doesn't have anything else either.

Andrew Hodgson