storing image to database

You probably shouldn't draw directly on the PictureBox.

You need to use a Bitmap instead. Try putting the bitmap in the PictureBox.Image and then call Save().

     private void button1_Click(object sender, EventArgs e)

    {

        pictureBox1.ImageLocation=@"C:\Documents and Settings\tr1g3800\Desktop\WALKING\30P\100000.jpg" ;

    }

    private void button2_Click(object sender, EventArgs e)

    {

        pictureBox1.Image.Save(@"C:\Documents and Settings\tr1g3800\Desktop\WALKING\30P\100000test.jpg",ImageFormat.Jpeg);

    }

    private void pictureBox1_Paint(object sender, PaintEventArgs e)

    {

    }

    private void button3_Click(object sender, EventArgs e)

    {

        Bitmap bmp = new Bitmap(pictureBox1.Image);

        Graphics gr = Graphics.FromImage(bmp);

        Pen p = new Pen(Color.Red);

        p.Width = 5.0f;

        gr.DrawRectangle(p, 1, 2, 30, 40);

        pictureBox1.Image = bmp;

    }