MAYBE THIS is a one off and won't work for everyone, but it might be worth a try. Recently my black cartridge on my old trusty hp 720C ran out. I was expecting it to, it had been in there for three years. On wandering round Akihabara I found some reduced because "the sell by date had expired" cartridges". Being cheap I bought a couple. When I got home and tried them out they wouldn't work, but being the inquisitive type (in addition to being cheap) I spent a little while ripping my hair out figuring what was wrong. After about an hour and a half I started to physically compare the old and new cartridge ..... and ......the copper pin layout on the new one was different. There was an extra pin! Scratched the pin off and voila. Sneaky hp.

Beebo