The cairo DLL in cairo-1.4.0-win32-only.zip is built with only the win32 surface and font backends. It has no external non-system dependencies. The cairo DLL in cairo-1.4.0.zip includes also the SVG, PDF, PS and PNG surface backends. It thus requires the libpng and zlib distributions from the dependencies subfolder. It is not built with the Freetype font backend, though. The same name is used for the cairo DLL in all configurations. This is on purpose. GTK+ 2.10 requires cairo with the PDF backend (because of the printing functionality). GTK+ 2.8 doesn't. The cairo 1.4.0 developer zipfiles are otherwise identical, but obviously the cairo-features.h file (which defines macros for each included surface and font backend) is different.