NT, Win95 and double buffering/flicker question

Hello,

I wrote an application in which two (overlapping) images are placed on a
panel and the property
doublebuffered is used to avoid flicker. On middle image I place a
raster image (bitmap drawn on image canvas),
the canvas of the top image is used to draw lines upon (the
Image.transparent property is set). I have some
questions:

How can I speed up the double bufferening? {*word*221}banding (using Xor) on
the top image is very slow!
I'am trying to tackle WMErasBKGNG...

If  I run my program on a NT machine the top images is displayed in
white! It covers the underlying image!
How can I prevent this. (it runs file on my Win95 machine)

Stephen