Microsoft has released the Technical Preview for Windows 10 this morning. Jump in, grab the installation ISO (available in multiple languages in 32 and 64 bit versions) and install. I recommend doing it on a VM or spare machine, not your production machine. There is always the possibility to lose data (rare, but I don’t like taking the chances).
Important
Remember, trying out an early build like this can be risky. That’s why we recommend that you don’t install the preview on your primary home or business PC. Unexpected PC crashes could damage or even delete your files, so you should back up everything.
If you want to stop using Windows Technical Preview and return to your previous version of Windows, you’ll need to reinstall your previous version from the recovery or installation media that came with your PC—typically a DVD. If you don’t have recovery media, you might be able to create a USB recovery drive.
After you install Windows Technical Preview, you won’t be able to use the recovery partition on your PC to go back to your previous version of Windows.