When I asked for IFR clearence for a flight going south and the windcoming from 300 ATC gave me runway 19 for takeoff. But shouldn't takeoff always be with headwind? Is this an error in FS9?

Not necessarily. It depends on the wind speed.

In genral yes you take off into the wind where possible but it all depends. some airorts you can only land and take off in the one direction. I did a flight on a Virgin Blue 737-700 a few months back and wee took off with a 5kts tail wind! That Air France Concord that crashed took off with a tail wind! But that was not a major factor in that crash.

>few months back and wee took off with a 5kts tail wind! That was also approximately my tail wind and I used the PMDG B1900D.At landing I was given the runway with headwind.

The only thing to consider in the sim is as the ground speed will be heigher, can you stop before the end? In reality, max tyre speeds and brake tempratures would probably be the limiting factors for more international airports with runway lengths obviously becoming more problematic at the regionals (assuming they are shorter, not always).For RL planning, the worst case scenario is usually considered to be a still wind as most airports have two runways so at most a 60-90 degree crosswind equates to a still wind and the worst wind conditions should one runway be blocked.