Android : How to remove title from custom dialogue box?

I am trying to implement custom dialog box. I created a seperate xml for custom view of my dialog box. Here i hate that big black bar ( Title bar ) present in that dialogue box. I need to remove that title bar and i want it exactly as in my xml file.

How to remove that title bar from dialogue box.??

Thanks in advance..

This is the about.xml for my custom dialog box.

<?xml version="1.0" encoding="utf-8"?>
<LinearLayout xmlns:android="http://schemas.android.com/apk/res/android"
    android:layout_width="match_parent"
    android:layout_height="match_parent"
    android:orientation="vertical" 
    android:background="#3BB9FF"
    >

    <TextView
        android:id="@+id/textView1"
        android:layout_width="wrap_content"
        android:layout_height="wrap_content"
        android:text="Author : M.Ganesh Babu"

        android:textAppearance="?android:attr/textAppearanceLarge" />

    <TextView
        android:id="@+id/textView2"
        android:layout_width="wrap_content"
        android:layout_height="wrap_content"
        android:text="This is my very first android game app..  Hope everyone like it. Contact me at kbxxxxxsh@gmail.com"
        android:textAppearance="?android:attr/textAppearanceMedium"  android:textColor="#FF7F3B" />

</LinearLayout>

This is the code i wrote in manifest.

<activity
            android:name=".About"
            android:label="@string/app_name" 
            android:theme="@android:style/Theme.Dialog"
            >