This means the key is activated on too many machines. LEGAL users can:
Using an unauthorized serial number is a violation of the End User License Agreement (EULA) and copyright law. While individual prosecution is rare, developers have the right to pursue legal action. Furthermore, reliance on pirated software deprives developers of revenue required to maintain and improve the software.
During installation, you'll see a field labeled "Serial Number" or "Activation Code." Enter the 20-25 character alphanumeric key exactly as provided. Copy-paste to avoid typos.