Texture Problem

Question

I am attempting to create a texture object with the following code texture = Direct3D.TextureLoader.FromFile( graphics, "greenbg.bmp", 0, 0, 0, 0, Direct3D.Format.Unknown, Direct3D.Pool.Managed, Direct3D.Filter.Linear, Direct3D.Filter.Linear, Color.FromArgb( 0, 0, 255 ).ToArgb() ); greenbg.bmp is a 640*480 bitmap but this code creates a 1024*512 texture!! If I change greenbg.bmp for a 32*32 bitmap it creates a 32*32 texture when I change this for a 512*512 bitmap it correctly creates a 512*512 texture!, can anyone tell me why it does not work with a 640*480 bitmap? (this is driving me mad!!)