Hi, I'd like to ask, how, exactly, does a user licence (i.e. serial numbers, activation codes) of a software, program, work in order to restrict the use and access to a single machine or user? If there exists a link which delves deep into the subject, it would be welcome, too!! Thank you!! ant01

With xp when you activate the OS it sends the key and some information about your computer to Microsoft. Now you can install xp on a second machine using the same key but when you go to activate it you will get the "License is already in use " message. If the machine dies, you can then call....explain and get it reactivated... IE, my motherboard fried and I had to replace it. There is also a retail version that can be used on any number of machines but only one at a time.

If you are specifically referring to the activation of Windows there is loads of information on www.Microsoft.com as to how it works. If you are referring to software in general there are many ways of doing it only limited by the ingenuity of the programmer. Stuart