The official GTK+ package only supports dynamic linking on Windows and even on other systems dynamic linking is normally only used.
The pre-built devolpment package for Windows has dynamic libraries only. If you really really want static libraries you will have to do a bit of hacking of the source code/configuration and build the libraries yourself.
Or try this site for pre-built bundles http://www.tarnyko.net/dl/
Is there a particular reason you must link against a static library? Note that there will be legal implications if you only release your code as closed source.