You could try these settings, they should run extremely light.
[PROXY]
EnableProxyLibrary=0
InitProxyFunctions=1
ProxyLibrary=
[GLOBAL]
UseEffect=0
AlternativeDepth=0
AllowAntialias=1
BugFixMode=1
SkipShaderOptimization=0
QuadVertexBuffer=0
EnableShaders_3_0=1
AdditionalConfigFile=
UseMRTRendering=1
TempF1=100
TempF2=100
TempF3=100
TempF4=100
TempF5=100
TempF6=100
TempF7=100
TempF8=100
TempF9=100
TempF0=100
[EFFECT]
EnableBloom=0
EnableOcclusion=0
EnableReflection=1
EnableMotionBlur=0
EnableWater=0
EnableShadow=1
DepthBias=0
EnableDepthOfField=0
[INPUT]
KeyUseEffect=123
KeyBloom=120
KeyOcclusion=121
KeyReflection=122
KeyCombination=16
KeyScreenshot=44
KeyShadow=119
KeyWater=118
KeyShowFPS=106
[REFLECTION]
ReflectionPower=3
ChromePower=6
UseCurrentFrameReflection=1
ReflectionQuality=2
ReflectionSourceSpecular=50
ReflectionSourceTFactor=50
UseAdditiveReflection=1
ReflectionDepthBias=0
UseLowResReflection=0
ReflectionSinglePass=1
UseEnvBump=0
EnvBumpAmount=100
EnvBumpOffset=100
ReflectionFlip=1
IBLAmount=6
IBLPower=5
[BLOOM]
BloomPowerDay=0
BloomFadeTime=0
BloomConstantDay=0
BloomQuality=0
BloomScreenLevelDay=0
BloomCurveDay=0
BloomPowerNight=0
BloomConstantNight=0
BloomCurveNight=0
BloomScreenLevelNight=0
BloomAdaptationScreenLevel=0
BloomAdaptationMultiplier=0
BloomAllowOversaturation=0
BloomMaxLimit=100
[SSAO]
UseFilter=0
OcclusionQuality=0
FilterQuality=0
DarkeningLevel=0
BrighteningLevel=0
IlluminationLevel=0
AdditiveIlluminationLevel=0
UseAmbientOcclusion=0
UseIndirectLighting=0
FadeDistance=0
UseForAlphaTest=0
UseForAlphaBlend=0
[COLORCORRECTION]
DarkeningAmountDay=30
ScreenLevelDay=15
ScreenLevelNight=0
DarkeningAmountNight=0
GammaCurveDay=0
GammaCurveNight=0
ColorSaturationDay=-1
ColorSaturationNight=-1
UsePaletteTexture=0
[WATER]
UseWaterDeep=0
WaterDeepness=0
WaterQuality=0
[SHADOW]
ShadowFadeStart=0
ShadowFadeEnd=100
ShadowAmountDay=30
ShadowAmountNight=55
ShadowScreenLevelDay=60
ShadowScreenLevelNight=20
ShadowQuality=0
UseShadowFilter=0
FilterQuality=0
ShadowBlurRange=1
[ENGINE]
ForceAnisotropicFiltering=0
MaxAnisotropy=0
ForceDisplayRefreshRate=0
DisplayRefreshRateHz=60
[MOTIONBLUR]
MotionBlurQuality=0
MotionBlurVelocity=0
MotionBlurRotation=0
[PERPIXELLIGHTING]
SpecularColorMin=0
SpecularColorMax=100
SpecularColorMultiplier=100
SpecularGlossinessMin=0
SpecularGlossinessMax=100
SpecularGlossinessMultiplier=100
[DEPTHOFFIELD]
DDOFQuality=0
DOFNumberOfPasses=0
DOFFocusRange=0
DOFBlurinessRange=0
DOFQuality=0
[PLUGIN]
WeatherMod=0