Thread: Help needed regarding JAVA Application Demo Version

Hi Every One,
I am a newBie in Java and this is my first post...on any forum.
I am working on an application that will REFUSE to run on a computer (Prints error) ,... IF the User has installed it second time (i.e. un-install and then installed 2nd time) i.e. Reached the license limit. The software may run on different MAC or Windows [All Versions].
I am working on NetBeans 7 IDE on windows 8 64-bit platform.
My Question Is:

Can anyone help what type of information is unique for every computer (e.g. CPU ID, Mother board Serial #). ?
How this information can be saved on my side... when the program is un-installed...?

I'm not sure if you're asking how to break an existing program's copy protection scheme or if you're trying to create your own copy protection scheme. Please clarify and know that we won't help you with the first.