How to remap keys when in Emacs

I am looking for a way to have my control key and caps-lock key switched when I am in the emacs window, but when I go to any other program such as Firefox I want to be able to use the normal control button for new windows, tabs and such.

Additional Information: I am using Ubuntu, but answers for all systems are good since someone else may want to know how to do it on their system.

From stackoverflow

• For globally remapping keys there is xmodmap. xkeycaps is an interactive tool. You can put control on both keys.

  Since you want to remap the keys only for Emacs (which I find somewhat ill-advised) you need to look inside Emacs for a solution. It should be possible, because you can rebind all keys, but it may be too tedious to swap all keys around if the modifiers cannot be swapped.

  Personally I map CapsLock to Compose, to type all kinds of funny characters like ä, ß, å, þ, «, —, ...

  Anton : The reason why I want it is because when I globally remap the keys and someone else uses the computer I am given non-stop shit for it.

• On windows using Auto Hot Key you can achieve this with this piece of code put in default script:

  #IfWinActive, emacs@      
      CapsLock::Control
  #IfWinActive
  

  Auto Hot Key is a very handy utility and it is also free software like in GPL.

• Emacs never actually sees the CapsLock keycode (under X anyway), so you can't remap the key in Lisp. Take a look at this page for details:

  http://www.emacswiki.org/emacs/MovingTheCtrlKey

• Maybe this helps. There is also a solution for windows without messing up with register.