/channelling Lady GaGa. Wow, that was unexpected.
So I needed to 'unrar' an archive...
Do I need to take a step back from that statement?
Fair enough, so 'RAR' is a kind of archive (where you shrink, or 'compress' a file, document, program, etc so that it takes up less space). Most Windows users will be familiar with ZIP files, well RAR does the same thing, only using a different compression algorithm.
XArchiver is a pretty good front end, and will automatically extract archives using the installed programs.
The only problem is that there is no 'unrar' installed. Normally I'd just 'apt-get' it, but that didn't work, so here is how:
Step 1: Open the sources.list file in leafpad:
sudo leafpad /etc/apt/sources.list
and add the following line:
deb-src http://mirrordirector.raspbian.org/raspbian/ wheezy main contrib non-free rpi
Then save and close leafpad.
Step 2: Enter the following into Terminal, in order:
sudo apt-get update
sudo apt-get build-dep unrar-nonfree
sudo apt-get source -b unrar-nonfree
sudo dpkg -i unrar_4.1.4-1_armhf.deb
Now (once you've rebooted) you should be able to use XArchiver to unrar your archives. Or you can do it from the command line (in Terminal):
(where 'file.rar' is the name of the file you want to unrar).