Code:
texture postTex1;

sampler postTex = sampler_state
{
   texture = (postTex1);
   MinFilter = linear;
   MagFilter = linear;
   MipFilter = linear;
   AddressU = Clamp;
   AddressV = Clamp;
};

float4 MyShader( float2 Tex : TEXCOORD0 ) : COLOR0 {
	float4 Color;
	Color = tex2D( postTex, Tex.xy);
	Color += tex2D( postTex, Tex.xy+0.001);
	Color += tex2D( postTex, Tex.xy+0.003);
	Color += tex2D( postTex, Tex.xy+0.005);
	Color = Color / 3.5;
	return Color;
}

technique PostProcess {
pass p1 {
	VertexShader = null;
	PixelShader = compile ps_2_0 MyShader();
	}
}

To put it simple: that is not a bloom shader.

A bloom shader should filter out the bright parts of the image, blur them and blend them back with the original scene. This just fetches 4 colors: the original pixel, and 3 pixels downright of it (moving away farther for each). Then it averages the color. It's just some weird kind of blur filter..

shader tutorial