zlib.dll not found
After downloading the latest win32-releases of ruby i was greeted with two error messages, SSLEAY32.dll not found and zlib.dll not found. The SSL library is kinda optional (gem, etc basicly work without it), but zlib not.
For this, the zlib library is needed, luckily there’s a native win32 port of it. So, download the latest win32 dll from zlib.net,
extract the zlib1.dll, rename it to zlib.dll and place it into the ruby bin directory.
SSLEAY32.dll not found
For SSLEAY32.dll the safest way i’ve found seems to use the version from the win32 postgresql client, which can be found here.
Just copy SSLEAY32.dll and libeay32.dll from the postgresql/bin directory into the ruby bin (or actually any other directory which is in your path)
readline.dll not found
Now you think everything is working, and start irb for the first time. Dang. readline.dll is missing. Readline win32 binaries can be found at http://gnuwin32.sourceforge.net/packages/readline.htm. Download the latest win32 build and copy the readline5.dll from the bin directory to your ruby bin directory again. Don’t forget to rename it to readline.dll.
Now everything should be working smoothly.