Dell P713w Printhead problem

I have a printhead problem and have followed all the instructions for getting it to work, but it still does not print and the printhead error on the printer will not go away--even after turning the printer off by disconnecting everything from computer and shutting down the computer.

This is the second time since I purchased it new that this has happened. The warranty ended 6-18-12 and I have had it not quite two years. The first time Dell replaced the printhead and told me to use 24 series cartridges.

Also, I was told my service tag was originally which is for a Dell v313w and now I am told it is for the Dell P713w. How am I to kinow which is correct if this service tag changes from one year to another?

Thank you for your help.