You should check the paperwork what was done to the laptop. It sounds like the motherboard had been replaced. Any major hardware being replaced will cause Windows 7 to do that. They should of known this would happen on an OEM system. It means that originally your system was installed with a OEM copy of Windows 7 which is used only once on a system build. They should have let you know this in advance. Most system's today are all OEM.
OEM versions of Windows 7 are cheaper copies of the OS that has no support etc and are used in single system builds. They typically run up towards $100 or so dollars for a OEM disc. It's a way to save some money building a new computer system keeping costs down. If hardware changes such as ram, hard drive, motherboard etc you can get a message like that as the system has changed and the OEM is not valid anymore. Microsoft takes a snapshot of the system. Many computer shops during the build process will use a beta free copy of windows to get the system built and running properly before installing the customers final OEM disc. You wouldn't want to install a OEM on a newly fresh built system incase something happens and the hardware is faulty and needs to be changed again during the build process.
There are also Retail copies of Windows 7 that can run up to $300+ dollars. Retail copies can be reinstalled over and over to any system, but not installed at the same time to multiple systems. If multiple system with the same key is used then the key will be revoked. Then there is the Enterprise Editions that can be installed on multiple computers at the same time because they came with licensing that is included with the disc.
Sorry for the long explanation, but you need to know what is happening here. On the bottom of the computer will be a Microsoft sticker with a product key code you need to write this down. Then call the Microsoft number it is a automated process to reactivate if that fails you can stay on the phone and talk to a rep. They may reactivate it for you for free. However, they may say sorry we can't do that and in worse case you need to buy a new OEM copy of Windows 7 Home, Pro, Ultimate which ever yours is. There should also be a #800 number on the sticker.
Some info on how to activate from within windows http://support.microsoft.com/kb/950929 or you could jump to the process of selecting country etc in that tutorial... by going to start and typing in slui 4 hit enter. By doing this it will generate a code and you can use that on the telephone system to activate. Good luck.
Edited by technonymous, 14 January 2014 - 07:56 AM.