How can I get the unique machine(pc) ID ?

You must use the Environment class in the System namespace. Whith this class you can get all information you need. You will find al kinds of information like: System.Environment.MachineName for the PC name System.Environment.OSVersion for the version of the OS Sysetm.Environment.UserName for the name of the current logged in user. and much more. Hope this helps you out, J.