Some people may have ever notice the alert message in Windows about the Activation message. The message will ask you to activate your windows in 1 or 2 even more days depending upon the time remaining for the activation.
This message is common and no need to be panic. This message is coming either your activation key has been expired or you are in the activation buffer period. For this message you need to give a valid activation key so that your version of windows get activated. You can even use windows without activation even after the expiry date, the only issue will be that, you will not get official windows update without the activation. Also you can use the system as earlier, no data will loss too.