gzdirect is missing in the zlib1 dll file. dll is a dynamic library link (It has to be linked to it to make it work correctly) You can try to search for it, and put it back in the folder or uninstall program, and download it again and reinstall. That should work.
Thank you for the helpful reply but I resolved the problem this week. after asking around in Gimper.net someone suggested to rename the zlib1.dll located in the win32 folder and copy the one from gimp into the win32 folder. i worried whether the action would affect the compatibility of my installed programs, so i kept the original zlib1.dll in the win34 folder. then i found Gimps miss placed zlib1.dll and returned it to its bin folder.