Command and Conquer Generals
From Widescreen Gaming Wiki
First, start the game & make all the desired changes in options & change the resolution to something other then 800X600(it's important!).
Then, Go into 'C:\Documents and Settings\%YOUR%20USER%20NAME%\My Documents\Command and Conquer Generals Data' open the file Options.ini' go to "Resolution = " & enter your desired resolution(i.e:"Resolution = 1440 900"). Save the changes then, right click the file, select Properties & tick/check "Read-Only". Thats it, enjoy.