Don't worry about that - it's just an inconsequential warning. It happens because ActiveState, in build 1003, used a version of Win32API::File that would best have been avoided. I'm told this will be rectified in future releases of ActivePerl.
It shouldn't be posing a problem for you (apart from the annoying message). If it does pose problems, please provide details ... or switch to a different build of ActivePerl.
(I've made some assumptions about your environment in the above. Please correct me if any of them are wrong.)