I love it when people reply without having a clue...
Anyway: BF2 doesn't support widescreen resolutions by default, but you CAN enable it via command line.
Start the game with this line, and it will work fine (create a short, and enter this line as "target"):
"x:\BF2folder\BF2.exe" +menu 1 +fullscreen 1 +szx 1280 +szy 800
Now, the game will start at the given resolution of 1280x800.
HOWEVER, if you go to your video settings, it will still show up as 1024x768, so do not change anything in there, as it will revert back to 1024x768. If you want to change detail settings, you will have to restart with the new shortcut after changing your settings.
If you have any similar questions regarding other games, I strongly advise you visit http://www.widescreengamingforum.com