it is answered in this thread:
http://www.widescreengamingforum.com/node/
Instructions (on Win XP Pro):
1 ) Install Q3 based game.
2 ) Run once, and quit, to generate the .cfg file.
3 ) Navigate to 'GameDirectoryBase' directory. (where GameDirectory is where you installed the game)
4 ) Right click the 'whatever.cfg' file. (for example: jk2config.cfg in JK2, q3config.cfg in Quake 3, myconfig.cfg in SOF2 etc...)
5 ) Select 'Open With' or 'Open' in the right click menu and then choose 'Wordpad' in the scroll list. Do NOT choose 'search on the net'. It's a waste of time.
6 ) You can either have the .cfg files associated with Wordpad or not from then on.
7 ) Use find (Ctrl-F) to find the string 'seta r_customwidth' and change the value in the quotes to read either 1680 or 1920, whichever res you have
8 ) The string 'seta r_customheight' should be below it, if it isn't, find it, ad change it to whatever value you want. E.g: 1050 or 1200.
9 ) THIS IS VERY IMPORTANT! Change the line 'seta r_mode' to '-1'. Otherwise it will ignore the settings and do its own thing.
10 ) Find the line 'seta cg_fov' and change the value to '115' or whatever you want. You can even set it to 360, but it looks like a fisheye lens. The exact Field of Vision is a matter of taste, so fiddle and find which setting you like the most! :D
11 ) Once these changes have been made, save them and start the game. Do NOT change the resolution in the settings panel, or you will have to edit the .cfg file again.
Feign posts where to find it
etmainprofiles(whatever user name)
works for me on my 1280x768 Syntax Olevia. Haven't found or added the seta cg_fov line yet so I'm gonna experiment some more but it looks great now.
also need to verify if it works on all punkbuster servers