Game Crashing & Freeze/Lag problem

[Luqkim]

Hi, I've been trying to replay Battlefront 2 now, and the game has been causing me lots of problems.

Whenever I start a battle, the game would go smoothly for about a few minutes.
Around 2 or 3 minutes of fighting later, the game suddenly starts to freeze or lags terribly and the game becomes totally unplayable.

Also, I can't seem to load Galactic Conquest or "Kashyyyk: First Line of Defence" mission, so I can't get pass that mission to continue the game.

I have both the CD and DVD versions of the game. I can play with the patch with the CD version, but the I cant patch the game with the DVD version (it'll keeps telling me I put in the Wrong Disc if I patch it).

Also, even if I do managed to finish a battle, the game will crash whenever I click "Done" and return me to my desktop.