Compaq C3-1000

When I recently installed a new black cartridge in my C3-1000 and I was going through the routine questions "New Black?, Right Black?,etc.", it went into a "Printer Error 0". I immediately unplugged the power supply cord, just as the product manual says to do, and re-plugged it in, to clear the error, but it didn't clear it.
I went and bought another new cartridge, and installed it, thinking I might have gotten a bad cartridge, but the error is still there. I also tried unplugging the USB cable and following some simple steps that a tech told me to try, but that didn't work either.
My next attempt to fix it was uninstalling the printer program and re-installing it, but that didn't work either. When I called COMPAQ, and tried to get some information to fix it, they told me that because my all in one is 6 months out of warranty, they couldn't help me and told me to buy a new one. Excuse me? I gave over $300 for it less than 2 years ago, I don't think it's supposed to give out this soon. Has anyone got ANY ideas as to how I can clear this error? I need to add that it doesn't even recognize that I have a new cartridge installed on the cartridge status window of the print program. I've also cleaned the printer head. Now I am at a loss as to what to do, and I desperately need my printer for the oil painting class that i teach. HELP!