This is a question I see on the forum fairly regularly. More often than not, the car has been advertised with power steering but the wheel is stiff to turn at low speed. The problem is that most car sellers don't really know. They just assume it has got power steering. Very few Fortwos actually have power steering as it was an optional extra.
However, what if your car does have power steering and it's just not working.
Turn the steering wheel anticlockwise (counterclockwise) as far as it'll go. Note the end position.
Below is a 451 without power steering.
And below is a 451 with power steering.
If the bottom of the steering wheel is pointing more upwards, you have power steering.
If the bottom of the steering wheel is pointing more sideways, you do not have power steering.
Working on it. A bit more tricky as the ratios seem to be the same for both types.
The majority of Roadsters do have power steering but there were some that didn't.
Open the bonnet and remove the front storage tray so you can see the steering rack.
The power steering rack has a larger part that the steering column attaches to.
This part has wires coming from it. If you have this, you have power steering.
Have a look here at ways to fix it.