I just posted a series of three messages at comp.periphs.printers,
asking about three solutions to the bogus "missing or damaged
cartridge" error message on the OfficeJet L7500/7600/7700 all-in-one.
Please consider this a pointer to those messages, asking about:
- the location of the CMOS battery in the AIO.
- how to "override" the expiration date, which HP officially declares
is possible, but then never
  tells us how to do.
- any magic key combination using the printer's keyboard, similar to
what users can do on
  PhotoSmart printers.

I've scoured the Web looking for a fix for this bogus error message,
and my three most promising fixes have all turned out to be dead
ends.  A fourth fix, editing the registry to change penwatch to 0000,
won't work in my case because I'm dealing with 7 computers running 4
different OSes.

--
Regards
Ray