It's probably going to be different per every game you want to do.
Looks like there is a "pcconfig.txt located in appdata in roaming for windows 7" that is the game configuration data.
Should look something like this:
FileVersion 3
ScreenWidth 1024
ScreenHeight 768
WindowWidth 1016
WindowHeight 697
WindowLeft 0
WindowTop 0
ScreenRefreshRate 60
VerticalSync 0
FSAA 0
AspectRatio 0
TextureQuality 0
SoftParticles 0
ForceMultithreadedD3D 0
IgnoreVendorPresets 0
Brightness 10.000000
SFXVolume 10
MusicVolume 10
MasterVolume 4
MusicEnabled 1
MouseSensitivity 10
InvertY 0
Vibration 0
BloomEnabled 0
ExposureControlEnabled 0
DoFEnabled 0
DesiredShadowMethod 0
ShadowsEnabled 0
DesiredDynamicLightQuality 0
SpeedBlurEnabled 0
MotionBlurEnabled 0
ProcessColourEnabled 0
WaterDistortionEnabled 0
EdgeAAEnabled 0
SSAOEnabled 0
RingEffectEnabled 0
LensFilterEnabled 0
AllowVendorExtensions 1
TTAnimationMode 0
UseHires 0
UseHiresPending 0
ForceShaderModel 0
You might try changing the resolution in that manually and see what happens.