I downloaded special forces from ea downloader and installed it , but when i start it up it says 'error mods/bf2/shaders/lightingfx not found' what should i do to fix it?

Try this,
go to C:\Program Files\EA GAMES\Battlefield 2\mods\bf2\Shaders_client.zip
or where ever your path is and copy Lightning.fx and Rain.fx

then paste them into here C:\Program Files\EA GAMES\Battlefield 2\mods\bf2\shaders

*IF THAT DOSNT WORK*

try to download/re-download the 1.3 patch (400mmb i think)

Cheers