Thanks for yout answer. It looks interesting but VS 2008 is needed to compile and I have VS 2010 and 2012 and the conversion of the solution to one of this two versions was not successfull. So I could not test it. If someone could compile one .exe from the sources of NVidia Textures Tolls I would be very gratefull.
Thanks.
I would like to convert a .png to .dds choosing dxt1, dxt3 or dtx5 in a script. So I need, if possible, the command line with the options to do it with paint.net or with another too that could do it. Thanks