How to activate Windows7

It means the windows is not genuine, or the disc you used to put windows on is not genuine,if the disc is then you need to activate it.
it should say on the start up page,when you get the warning come up look for were it says activate this set of windows then press activate,it will then go and see if the windows you are running are genuine,if not u will have to buy a windows disc that has got the windows key to put a new set of windows on.