Hello, thank you all for your responses. I've been a few days on hollidays and didn't watch them. I've had few time to work on the program, but it already has several interesting features: we already know how long is the file we are playing and for what position we are, hence it would be easy to add a track bar.
In the other hand, it can play several formats, including films avi, you can check it. Also can play in a loop if you click in the 8th button (loop icon) or just one time if you click it once again.
Nevertheless, i have to control better when the file ends playing and polish many things.
Also, i'd like to add an oscilloscope bar, but this seems to be not so easy to implement, though this is a main point to me because, controlling this, can be used in demos for sincronizing graphics and sounds.
My objective is not to make a multimedia player in the usual way, just play a bit with sound programming.
I think that it is amazing you can make a simply (but functional) multimedia player in a few kilo bytes.
Regards