What should I do if Windows 10 upgrades 80240020?

In general, the upgrade of Windows10 is quite smooth. There is no big problem, but it is impossible to have no problems. When someone upgrades from Windows 8.1, the installation will fail and give an error when the download is completed. Code 80240020, what does this mean?

Microsoft said that the Windows 10 upgrade is for global users, the scale is too large, so it can not be pushed all the way in the first time, only in batches.
If you see the above error message, it does not mean that you have any problems with the upgrade itself, but it is too busy at present, you need to wait a little longer, especially if you use some techniques to force the upgrade, it is more likely to occur. .
If you have to upgrade, there is no way, just open the registry and locate it:
HKEY_LOCAL_MACHINESOFTWAREMicrosoftWindowsCurrentVersionWindowsUpdateOSUpgrade
Create one without this item, then right click in the blank area on the right, create a new one DWORD (32-bit) value, and named "AllowOSUpgrade", and then change the value to “1”.
Next reboot and open Windows Update again, check the update, you can start.