Good question to post on an US board where every single spoiled customer has power windows as a standard feature ever since the early 70s...
You euro 1996 C class has NOTHING at all as far as the power windows go (BTW: like your sig-picture!).
The power windows get their power from the additional fuse box that is mounted in the trunk (near the battery). Not every Euro C class has this additional fuse box though; it depends on the fact whether your car has a sunroof and/or power seats that are fused there as well.
The power windows share a relay with the power sunroof. The relay (big and expensive) is mounted in the chassis beam behind the battery (in case you want to look for it). The relay is different for sunroof-only cars/power front windows/power front and rear window cars...
There is absolutely no wiring available and you will have to put it in all by yourself (nice job to do though
). I have bought the four power window mechanism new for my car (OEM MB) for about 1200 Dutch guilder (approx. 520US$) and that was for the mechanisms with the motors only. My car already had a power sunroof, so it already had a fuse box and a relay in the trunk (not the right one to combine with power windows) to cope with the auto-closing feature that mercedes has on their cars.
The AMG interior I bought came with the complete wiring, all switches and all relays of the donor car, which made it fairly easy for me to install the 4 power windows (didn't want to cut holes in the leather door panels for my manual window handles).
Mike C200 (benzsport member) has installed OEM rear power windows in his car that already had the front power windows from the factory.
Long story, I am sorry...but this is about what I can tell about adding power windows to a 1996 Euro C class...No, that is not all:
If you decide to get some parts from car recycle shops, you have to know that the pre 95 electrics were completely different (different shape of switches and different set up for the switches as well (partly separate switches).
The after 97 models (since the model change) are not usable for your car either. The 97 and newer C class has a complete switch panel (4+1 window, 1 side mirror and 1 trunk lid release switch) that only has 7 or 8 wires and a relay in every single door.
The 1995-1997 (up to the model change) switch panel consists out of 4+1 window and 1 side mirror switch (it is a complete panel so you will not need the current side mirror switch anymore).
However...if you consider going after market...it will be a lot easier. If you do want to go aftermarket, you have to be sure that you use proper fuses and OEM switches (after market switches are NEVER as good as the OEM ones). You can order OEM switches and connectors at every MB dealership without any problems (I can get you the part#s).
If you want to go after market...I might have a set of front power windows for you (for whatever reasonable price you want):
The tag says ->8,95 but that is because of the shape of switches. The set comes with the wiring and covers for the door panels...forget about the switches in the package.
(I hope that I didn't scare you too much, but it really is a hassle to add power windows when your car has nothing and you need to buy it all OEM)