Microsoft has released Windows 10 technical and enterprise previews to the public, if you want to try the new version of Windows,
For users of Windows 10 Technical Preview, which can be found on the Windows Insider ISO download page. When installing Technical Preview, use the following key toWindows 10 KEY:
NKJFK-GPHP7-G8C3J-P6JXR-HQRJR
The enterprise Technical Preview does not require a key to install, but requires a key to activate. The following key can be found at the TechNet evaluation center KEY link:
PBHCJ-Q2NYD-2PX34-T2TD6-233PK