The dep_walker is small utility gem that checks dependencies for native extensions used by installed gems on Windows. If you are {RubyInstaller}[http://www.rubyinstaller.org] user and have seen message box: <em>"This application has failed to start because <name_of_dll>.dll was not found. Re-installing the application may fix this problem"</em> when you tried to use gem that has pre-built binariy extension, you've faced common problem on Windows systems - missing dependency dll. Same error might occur even if extension library was built during gem installation if all header files and libraries are available to the build tools, but runtime dependencies are not present. With dep_walker you can simply check all installed gems. Even more, if log is turned on, gem will print out information where dependency is found on the system, so you can check whether Ruby extension really uses correct version of required dll.