1. Download the clustalw-2.1-win.msi from http://www.clustal.org/download/current/.
Launch the installer by double-clicking the clustalw-2.1-win.msi. Please follow the instructions to complete the installation.Clustalw2.exe is created in [C:/Program Files (x86)/ClustalW2].
2. If ClustalW Ver.1, download the clustalw1.83.XP.zip from www.clustal.org.
When you unzip the clustalw1.83.XP.zip, you can get the clustalw.exe file.