ros-hydro-desktop-full : Depends: ros-hydro-simulators but it is not going to be installed [closed]

edit

I am trying to install ROS on ubuntu 12.04 to use it with both gazebo and morse.

I first installed ROS fuerte, but the setup.* files were not created in /opt/ros/fuerte. So I removed ROS fuerte and tried to install ROS hydro. when typing sudo apt-get install ros-hydro-desktop-full an error occurred:

user@user-SATELLITE-L750:~$ sudo apt-get install ros-hydro-desktop-full [sudo] password for user: Reading package lists... Done Building dependency tree
Reading state information... Done Some packages could not be installed. This may mean that you have requested an impossible situation or if you are using the unstable distribution that some required packages have not yet been created or been moved out of Incoming. The following information may help to resolve the situation: The following packages have unmet dependencies: ros-hydro-desktop-full : Depends: ros-hydro-simulators but it is not going to be installed E: Unable to correct problems, you have held broken packages.

How can I resolve this ?

thanks in advance