The BC.ICO file only contains 1 icon.

The ICO file format specification says that an
ICO file can have one or many images:

http://msdn.microsoft.com/en-us/library/ms997538.aspx


The interesting fact is that the
ICONDIRENTRY.dwImageOffset field doesn't contain
an offset into the file where the image
begins, but instead it contains the ID of the
ICON resource in the EXE's .rsrc section.

It's rather easy up to this point but it would
be a little bit more difficult to make all of
it automatic for our own resource compiler.


The other option would be to use a third-party
resource compiler and convert it into a proper
binary .rsrc section, as we did here.

The good thing is that at our pace, we will
have time for learning several other Windows
things.