For $1200, you will have difficulty finding a laptop that can reliably play the game on huge maps into the modern age... I gather that the game is very Graphics intensive and that a standalone graphics card is almost essential and I don't know of any laptops in that price range that do not have on-board video.
I just spent $1,650 (including taxes and shipping) on a laptop just to play the game (but I did give my wife the excuse that I would do some work on it) !
Dell Inspiron 9300 with 1.73 GHz Pentium M, 2GB Ram, 17" UXGA screen, 60GB-7,200rpm Hard Disk, GeForce Go 6800 Graphics Card and 9 cell battery (I gather the 9300 has short battery life even with the Pentium M).
That was with a $750 coupon (do a web search for dell coupons). I think that base price has to be $2,000 for the coupon to apply and taxes/shipping will add up to $150 depending upon where you live. So, you can probably get it down to about $1400 by selecting some combination of the 6 cell battery, the 5,400rpm Hard Disk, the non-TrueLife screen and only 1GB of RAM.
I would recommend that you keep the 2GB of RAM if possible since it will avoid most memory paging and improve performance on anything memory intensive (and future software will only get worse !) The faster hard drive improves loading times by up to 40%, but this is mostly only relevent when you startup or do a save if you have enough RAM to avoid paging. If you are going to be mostly plugged in, the 6-cell battery will be fine - it only runs about 1 to 1.5 hours when playing games since the screen and graphics card suck juice. There are different opinions on the True-Life screen.