I open my drupal forum using the following link:

http://localhost/drupal/forum

Now I see all container. One container is called "General discussions". I click on "General discussions" and the browser is redirected to :

http://localhost/drupal/?q=forum/2

Ok is good. Now I see all topic (thread), I click on first topic and my browser is redirected to :

http://localhost/drupal/?q=node/2

The last link (http://localhost/drupal/?q=node/2) is wrong because I want to access something like : http://localhost/drupal/forum/topics/2
I don't want to leave the "/forum" string in URL. Please tell me what I need to do to solve this issue ?

Thank you very much !