KotOR Galactic Conquest is a mod you can add on to Battlefront - if you have the Conversion Pack 2.0 and the newest version of the Unofficial 1.3 Patch (r117 -Starwarsbattlefront.gamefront.com ) - that lets you play the "Galactic Conquest" gamemode with new sides and a new planet setup.
There are two ways you can play. The "Jedi Civil War" Galactic Conquest lets you play as the Old Republic and the "Advent of the Sith" lets you play as the Sith Empire. Both of these use the KotOR era from the Conversion Pack 2.0, and both of these use a lot of the Conversion Pack maps. One of the new parts of this Galactic Conquest is that when you go to a planet - say you go to Tatooine - you may end up on any of the Tatooine maps - Mos Eisley, Jabba's Palace, or Dune Sea. The KotOR GC also adds a few new planets to Galactic Conquest - Alderaan, Bespin, Rhen Var, Ord Ibanna, and the Star Forge system (which is the Sith's capital system).
In addition to the tweaked map content, there's some new stuff as well. One of the cut bonuses from the final game - the "Sensor Array" bonus, which reveals all the units on the field - is added back in as a purchase-able bonus. There's also a brand-new space map ("Space"), which is used for all the KotOR space battles (except for the Star Forge battle). It features a random skydome, so it doesn't always look the same whenever you start it up.
As long as you follow the installation instructions carefully, this should be a cinch to download and use. It's not a large file, and there are a number of documents to help you install and use it correctly. Be sure to check it out - and look in our media section, we added some shots of the interface!