I went to Sears today and had a new battery put in the car. Afterwards
I noticed that my stereo is no longer working, nor are my running
lights. The stereo and lights are both after market additions, but I
bought the car used and don't have any documentation for the equipment
or the work that was done.

All I know at this point is:
1) Lights wont work, except when I press 'unlock' on my key control -
at which point the lights will flash twice if the switch that controls
them is engaged.
2) Stereo does nothing. It normally rolls into the dash when I turn
the ignition off and comes out automatically when I start the car. It
doesn't even roll out.
3) The switch that controls the lights is labled PIAA (as is some of
the additional wiring that is connected to the battery). When I press
'unlock' the little led on the switch will flash twice. If the switch
is on, the running lights also flash and the led flashes green. If
the switch is off, it flashes red and the lights don't flash at all.
Either way, I can hear a distinct clicking sound when this happens
that seems to originate from some electrical equipment under the
passenger side dash. This is near the fuse box on that side, but it
doesn't come from the fuse box. This click is new. Didn't happen
prior to the battery install.
4) I don't think any of the fuses in the passenger side fuse box are
bad. In particular I replaced the one that is for the stereo with a
known good fuse and nothing happened.
5) The guys at Sears told me they thought there might be some sort of
kill switch or other security device that was affected by the removal
of the old battery. They couldn't find it. I couldn't either and no
one told me about such a thing when I bought the car.

If it makes any difference, the car is a 2000 Accord.

That's about it. I'm not very car savvy or very stereo savvy and so
I'm about out of ideas. My next thought was to take it to a local
dealer who installs stereo systems and let them look. But I thought I
would run it past you guys and see if someone knew an easy solution
or, if not, if you have any idea what's wrong and how much it might
cost to fix...

Thanks,

Rusty