wget or curl executables not found. Curl activated but not working
The problem was with the php.exe path in drush.bat

The solution is to properly edit it. In my case ( I use xampp ) here is the path: 

@echo off
REM See http://drupal.org/node/506448 for more information.
@c:\xampp\php\php.exe "%~dp0drush.php" %*