Store string in c# application which does not change after first time, c#-4.0, c++, windows

I have a application developed in C# and I want that the first time when user open the application it stores the key, user system mac address and system ip in a variable and whenever user again open the application I can find the first entered data which was stored. But i don’t want to store it on the users system that he can edit that. Do we have any option to do it in the application it self.

Source: Windows Questions