If you currently have legitimate access to Game Maker 8 Pro you can use your Softwrap Purchase Reference number to generate a GameMaker 8.1 License key.
To do so click here to visit the YoYo Game Store and press the “Upgrade” button. You will be prompted to enter your purchase reference number for Game Maker 8. If you don’t know what your purchase reference number is you can request it to be emailed to you at Softwrap.
Once you’ve entered the purchase reference number at the YoYo Game Store a $25.00 upgrade discount is applied which makes the purchase free.
You are then presented with your GameMaker 8.1 License Key which should be entered into the software alongside the email address tied to your YoYoGames.com account. The form for doing this is located under the Help menu.
When your valid details have been entered the software instantly upgrades to GameMaker 8.1 Standard.