Carlos wrote about an HP 1000 E-series:
I have not been able to open the front panel
latch because I do not have the key, so I don't know
what's in the front card cage;
One of the screws behind the front panel "flange", when removed, will
cause the panel latch assembly to fall to the bottom of the machine,
and the front panel to flop open. It is then a simple matter to remove
the lock and take it to a locksmith to either get a key made or get it
rekeyed. It's also very easy to reassemble.