Hi Peter,
It could be several things. For example:
1: Declaration of ChoosePixelFormat
2: Is #case capital being used .. PFD pfd.
my ImgWin.inc uses #case capital for the C style headers and this can be disruptive if some of the symbol names are capitalised in some places but not others. I have had to rework some of my examples when adding imgwin/GDIplus for this reason.
Charles