It asked for a license key, where can I get one from?
You need a "windows Live" ID if you don't have one just open a HotMail account and you will get one. Then as
Bushfiva says go to the download page:
Windows 7 Release Candidate and it will click and set your desired language click on the arrow and the next page will ask you to sing in using your password it will then E-Mail you the serial number and allow you to download.