Just out of interest, I have been refilling my chipped HP cartridges for the last 22 months and they still work as good as new.
The trick is to not let the printer know that the cartridges have been removed.
This is done by switching on the printer, opening the drop-down door so that the cartridges move to the centre and are ready for removing. At this point pull the mains plug for the printer out of the socket, remove the cartridges, refill as necessary and then replace cartridges in the printer.
Now you can replace the mains plug in the socket and close the drop-down door.
The printer will still occasionally tell you that the ink levels are low but this is just ignored as you should now be fully aware of how full/empty the cartridges are. I check mine every couple of months to make certain that they are never, ever run too close to being empty.
I thought other people with HP printers who wished to re-fill and were being foiled by the in-built microchips might be interested in this.