Backbuffer trouble

I've been trying write a small module which serves as a 'wrapper' for the GDI functions like BitBlt, LoadImage, etc. The functions return simple structures ('surfaces') so they can be accessed and removed by just passing the structure.
Using this method I also created a backbuffer, but the real problem is when I copy the backbuffer to the main form, nothing appears. Here's the file including the images and code: http://home.wanadoo.nl/dennis.meuwissen/temp/Plat.zip

Could anyone help me out with this?