This means you got a binary distribution of some module (probably either Win32::SerialPort or Win32::API) that was built for a different binary distribution of Perl other than the one you are using. Try this:     perl -MWin32::API -e 0 if it doesn't give you an error, then it is a different module that is the problem. When you find the problem module, uninstall it (if possible) and then find a distribution that was built to work with your distribution of Perl (sorry, I'm not familiar with how these modules are currently distributed in binary format -- part of the problem with trying to create a distribution system outside of CPAN like has been done with Win32 binary distributions of modules).