http://www.triniti.co.uk/Demos/

got some demo files in there.. but dunno how to open it :\

how u wanna watch the demo? u got the map already?

teach me how to open it

The Community section of BF2 has two sub-sections:

Battlerecorder: The Battlerecorder allows you to play back demos which have been bookmarked from particular servers you've played on which have Battlerecorder enabled, and those which you have saved in your Battlerecorder Library. These demos contain full footage of your gameplay during a particular round. Battlerecorder is an option which must be enabled by servers, and can't be used to record games by clients (i.e. regular players). More details of Battlerecorder functionality can be found here. To record and play back your own custom demos see below:

Creating Demos: To make a custom demo of any length, you must be in Singleplayer mode, or on a server of your own creation (See Local Servers below) - you can't record your own demos on Multiplayer Internet servers. To start recording a demo, use the demo.recorddemo [demoname] command in the Command Console (See the Advanced Tweaking section). When you want to stop the demo, use the demo.stoprecording command in the console. Your demo has now been saved as a [demoname].bf2demo file in your Program Files\EA Games\Battlefield 2\mods\bf2\Demos\ directory.

Playing Back Demos: To play back a custom-made demo in Battlerecorder, you must copy your demo into the \Documents and Settings\[username]\My Documents\Battlefield 2\Profiles\Default\demos\ directory (if that directory doesn't exist, create it under the Default profile directory). Then when you go into the Battlerecorder section of BF2, you will find that the demo is listed under the 'Battlerecorder Library' area, and you can simply highlight it and play it from there. Thanks to Ryan Nichols for this tip.

If you want to launch the demos from outside BF2, download my BF2DemoPlayer.zip file (4KB). Once downloaded, extract the contents and place both files in your base BF2 directory (typically \Program Files\EA Games\Battlefield 2) - this is an important step, as the player won't work correctly if run from any other directory. These files are a slightly modified demo.cmd file from EA Games, which you can read more about here, and a custom batch file I've made called BF2DemoPlayer.bat. To play back any demo using these files, first make sure the demo is in your \Program Files\EA Games\Battlefield 2\mods\bf2\Demos\ directory. Then run the BFDemoPlayer batch file, follow the instructions given and your demo will be launched in your chosen resolution. You can stop the demo at any point either by opening the in-game console and entering demo.shutdownDemo, or by pressing the Q key and selecting Quit.