Did the laptop come with Windows 8 or did you buy Windows 8 and installed it on the laptop?
If you installed Windows 8 onto a device you can call MS and there used to be a way for you to remove the activation from one device and move it to another, the down side is your computer currently running Windows 8 will now not be able to there fore looses the Genuine Windows.
If the computer came with Windows 8 yes you did still pay for the OS, but it is a OEM version which means non transferable, it is a different license and usually cost the OEM a lot less for the license.
It has always been 1 license per computer. Remember that stunt that MS was trying to pull way back when multiple cores came out. They wanted you to buy a license for each core. LOL. The government told them NO WAY.