As Om Nom Nom said, if the windows came pre-installed on your machine it is most likely an OEM copy. Which basically means it will only authenticate to your current machine. If you bought your copy of windows 7 you can just install to another computer and authenticate. You might have to use the phone route tho. According to the EULA
- TRANSFER TO ANOTHER COMPUTER.
a. Software Other than Windows Anytime Upgrade. You may transfer the software and install it on another computer for your use. That computer becomes the licensed computer. You may not do so to share this license between computers.
Microsoft asks that you format the old hard drive. But basically once the old laptop goes to check for updates and a Windows Genuine Check
happens it will be de-authorized.