I also always wondered what they did with Commander Data's internals when STNG ended.
Going a bit off topic here being a major Trek fan.
To answer that question I suggest you watch the movie Star Trek Nemesis.
Or you can read the spoiler I posted below. The spoiler also reveals some things for the game Star Trek Online in that regard.
I post it as a spoiler as I know how it is when someone tell you what happens, this way I dont spoil it for those who want to find out for themselves.
[spoiler=Star Trek Nemesis (movie) & Star Trek Online (Game)]In the Movie Star Trek Nemesis, they kill Data at the end.
He sacrifices himself to destroy a Romulan weapon of mass destruction and save his Captain who is ready to sacrifice himself to do the job.
If you played Star Trek Online, Horrible game btw and should never have been made that way, you will see they revived him again.
I for one dont like it, but it is said they used the android Data himself created called B4 to revive him.
But technically speaking with Data destroyed they have no way to transfer Datas knowledge to the new body, which is why I dont like that plot line[/spoiler]
To get back on topic, looking at those pics I had to ask myself if that was really a computer. Looked more like a jumble of cables, wires and components to me.