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?

Well that's not the usual pile of stuff in the junk box.
But I would hasten to add that there's probably no "usual" stuff in any box.
A quick look around my desk shows: - a yoyo. - 2 45 volt batteries. - a small CO2 tank (paintball) - one of those dog collar electronic receivers. - proto board with some Atmega suff. and various other junk.
That doesn't include the rest of my shop where I have everything from a laser to a variety of machine tools.
I usually try to strip out parts from things like printers, cameras.. and toss out the shells and bits like specialty pc boards.
Whenever I start to trip over everything, I sell or give away enough to continue with my bad habits. :-)
DOC
Buys junk. Screws around.
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