Like what Pfile said but with a bit more details:
4. Installing PixInsight on Several Computers
The commercial End User License gives you the right to install PixInsight on any computer you own, and on any supported platform (Linux, Mac OS X, and Windows). However, you should understand how PixInsight licenses work in order to carry out multiple installations correctly. Knowing this is also very important in the event you need to reinstall PixInsight (because you substitute your hard disk, for example).
The first time you install and activate your copy of PixInsight, it will create a special license file on your hard disk, as we have seen on Section 2 above. Considering the importance of this topic, let us repeat part of the information already given there. The license file has the following name:
Linux and Windows:
.pixinsight-license
Mac OS X:
pixinsight-license (note that having the file named .pixinsight-license works too in that location.)
and is located on your personal folder. Normally, your personal folder is at the following locations:
Linux:
/home/<your_user_name>
Mac OS X:
/Users/<your_user_name>
Windows Vista:
C:\Users\<your_user_name>
Windows XP:
C:\Documents and Settings\<your_user_name>
where <your_user_name> is your actual user name on your operating system.
