HP Deskjet 840c Grayscale Problems

[wwtoonlinkfan]

My decade-old HP Deskjet 840c recently lost its ability to print in color (i.e. even with a full color cartridge, color won't print). So I switched over to grayscale mode, and the printer printed full-grayscale images with just the black cartridge and an empty color cartridge (the printer refuses to work without both cartridges). However, the black cartridge stopped working even though it had ink left in it, so my father got a remanufactured cartridge. The cartridge also worked fine with grayscale, but when I changed the settings to see if the color worked again, the printer refuses to print in true grayscale. I use the HP official Windows XP drivers from their site, and I tried all three grayscale settings (High Quality, Black Only, and Optimize for Photocopy or Fax) to no avail-the printer only prints the darkest shade of black. The crazy thing is that the printer actually printed in grayscale when I first got the new cartridge. In HP Preview mode, the image shows up as true grayscale, but the print output is not. Please help me with this. We can't afford a new printer and our current one worked just fine before.