Recycling components for robot construction.

I'm very new to robotics.  I've read in a few places that it's best to
start off with all-new components.  But after a while, one may recycle
components from previois robots and from other electronic equipment.

I have a load of old electronic stuff cluttering up my flat.  I've
never got round to taking to it the tip.  Bow I'm wondering if any of
it might be useful.  A cursory glance reveals this (though I'm sure
there's more):

AC/AC adapter - model MW48-1201100UKA
Input:230 V AC 50 HZ
Output:12V AC 1100 mA
CB APPROVAL NO:SE 1200

Canon AC adapter - AD-150C
Input:240 V ~ 50 Hz   140 mA
Output:9.5 V - 1.5 A   15 VA

Turntable (from separates stereo system)
Cassette tape deck
Stereo audio amplifier
An old image scanner (with lead that plugs into PC's printer port)
Length of co-ax cable.
A lap-top computer that was killed by coffee. (it didn't get drenched
- but some must have found its way inside.

The stereo equipment doesn't work (though they do light up).  Assuming
that there are usable components, how can I find out if the parts are
in working order?