Stuck on Problems with my game.

You mean you want the lighting shader to shade your textures instead of vertex colors? In that case, try thsi:

//Cg
//
//Cg profile arbvp1 arbfp1

void vshader(float4 vtx_position   : POSITION,
             float3 vtx_normal     : NORMAL,
             float2 vtx_texcoord0 : TEXCOORD0,
             out float4 l_position : POSITION,
             out float2 l_texcoord0: TEXCOORD0,
             out float4 l_brite    : TEXCOORD1,
             uniform float4 mspos_light,
             uniform float4x4 mat_modelproj)
{
  l_position = mul(mat_modelproj, vtx_position);
  float3 N = normalize(vtx_normal);
  float3 lightVector = normalize(mspos_light - vtx_position);
  l_brite = max(dot(N,lightVector), 0);
  l_texcoord0=vtx_texcoord0;
}


void fshader(float4 l_brite     : TEXCOORD1,
             float2 l_texcoord0: TEXCOORD0,
             uniform sampler2D tex_0 : TEXUNIT0, 
             out float4 o_color : COLOR)
{
  if (l_brite.x<0.5) l_brite=0.8;
  else l_brite=0.9;
  float4 texture=tex2D(tex_0, l_texcoord0); 
  o_color=l_brite * texture;
} 

I didn’t try it, though it should be working. Let me know if not.