Question: how to install rxtx in windows?
Answer: unpack rxtx-*-win32.zip,
copy rxtxSerial.dll to %JAVA_HOME%\bin, (%JAVA_HOME% is the folder where JRE is installed on your system; e.g. c:\Program Files\Java\j2re1.4.1_01)
copy RXTXcomm.jar to %JAVA_HOME%\lib\ext.