I tried to install PR2 simulation on Indigo but i get the command like this --- E: Unable to locate package ros-indigo-pr2-desktop -- What should i do?

edit

Edit: not sure what the current status is, but at least at the time of answering Unable to locate package ros-indigo-pr2-desktop pr2_desktop was not being released any more.

Ignoring that, your ROS install has a problem. See below.

N: Ignoring file 'ros-latest.list.' in directory '/etc/apt/sources.list.d/' as it has an invalid filename extension

I don't know whether the rest of your configuration is correct, but the error message is clear: apt is ignoring your ros-latest.list. because it does not have the file extension it is expecting.

Apt only loads files (in this case at least) with the extension .list. Your file has an extra dot (.) at the end: .list..

Just remove that dot, and things should work a little better.

Suggestion:

sudo mv /etc/apt/sources.list.d/ros-latest.list. /etc/apt/sources.list.d/ros-latest.list

Then try sudo apt-get update again. After that you can try to install the package (that won't work, as the package hasn't / won't be released, but other packages should now work).