Hello Najib
It seems to be a problem of installation of telemac. You need to add your telemac path (I think for you is C:\opentelemac\V6P2\config) to the environment variables of your computer (write environment variables in "search programs and files" and windows will find it for you).
A more easy way is to use the new auto-install tool which does all the job for you.
You will find more hints on the windows part of the forum
www.opentelemac.org/index.php/kunena/2-windows-version and on the installation rubrique of the website
www.opentelemac.org/index.php/installation
I hope that this is helpful,
With my best regards,
Riadh ATA