Being an avid Steam user I refused to accept that the Crysis Wars SDK and Sandbox editor would not work properly with the Steam version of the game. Turns out that the only real problem is that Steam installs the game in a different directory than Crysis Wars expects, so the solution is pretty simple. Crytek even included a tool so you wouldn’t have to go mucking around in config files.
To get started, go ahead and download/install the latest version of the Crysis Wars SDK if you haven’t already. It should detect that Crysis Wars is installed in the Steam directory.
Then, browse to “C:\Program Files\Steam\steamapps\common\crysis wars\tools”. Note that on 64-bit systems it will be “Program Files (x86)” instead of just “Program Files”.
Double click the ‘SettingsMgr.exe’ program.
In the ‘CryENGINE2 Settings’ window, set the ‘Root Directory’ to “C:\Program Files\Steam\steamapps\common\crysis wars”. Once again replace “Program Files” with “Program Files (x86)” if you are on a 64-bit system.
After clicking the “Ok” button you should now be able to work in the Sandbox editor with your Steam copy of Crysis Warhead/Wars!