Improved Game Performance

Open uoconfig_mp.cfg with WordPad - you will probably have to run WordPad as administrator for changes to take effect.
There will be a copy of
uoconfig_mp.cfg in the uo directory/folder, and also in any mod folder.

To use custom settings for widescreen monitors:-
seta r_mode "-1"
seta r_customheight "1080"
seta r_customwidth "1920"
Obviously, substitute your monitor resolutions where I have 1080 and 1920 ........
Some guides will tell you to change FOV also.  This does not work on CODUO.  FOV is hardcoded at 80.

Allow the game to use a greater amount of computer memory
seta com_hunkmegs "512"
By default the game uses 128mb.  Modern computers have much more memory available.  Setting to 512mb allows faster map loads and smoother play.

Improve Network performance
seta snaps "30"
seta cl_maxpackets "100"

seta rate "25000"
There are a number of variations to this - Google is your friend.  These settings work for us.

Make sure your graphics drivers are up to date, from the manufacturer's website.

Depending on UAC settings when you installed the game, the cfg files you need to  edit may be in
Users/yourname/AppData/Local/Call of Duty Game Of The Year/uo
Also, Windows 7 seems to have issues downloading custom content, if game is NOT installed to the default directory/folder.

Edit uoconfig_mp.cfg
There will be a version of uoconfig_mp.cfg in the uo folder AND any mod folder.  To change settings for the Phoenix server, make sure you change the version in the Phoenix folder.
Right Click on your CODUO Multiplayer ICON on your Desktop.
Go to the "Compatibility" tab, check "Run this program as an administrator".
This will force the custom maps etc to download to the game installation folder, instead of your localapp.