How to uninstall Win10 system preview version

After the Windows 10 preview release, many people can't wait to install to experience new features. But this is not the official version after all, and many functions are still in the testing stage, so it is not so satisfactory. So it is inevitable to return to the original system. How to uninstall Win10 Preview?
If you are running Windows 8, and you are using this preview version installed by ISO, you will not be able to uninstall it. You need to reinstall Windows 8 using the recovery or installation media that came with your computer. If you don't have recovery media, you can create a USB recovery drive.
If you are running Windows XP, Windows Vista or Windows 7, you cannot uninstall this preview version. To revert to the previous operating system, you will need to reinstall from the recovery or installation media (usually DVD media) that came with your computer. If you don't have recovery media, you can use the software provided by your computer manufacturer to create recovery media from your computer's recovery partition before updating. After installing Windows 10 Preview, you will not be able to recover from previous Windows versions by using the recovery partition on your computer.
If you are currently using Windows RT, you will not be able to uninstall the Windows 10 Preview, and only upgrade to the official version of Windows 10 when the final release is released.
Speaking so much, to sum up, Win10 preview version can not be uninstalled, can only reinstall the original system, instead of Win10 preview version. The official version of Win10 will be launched in April 2015, and it is actually faster.