There is nothing scarier than installing Windows 10 on your machine and coming up with an error message. If you see error 80240020, it means that something in your Windows 10 installation folder is either corrupted or didn't complete. Here's how to fix it.
1. Go to C:\Windows\SoftwareDistribution\Download and delete everything in the folder.
2. As an administrator, run the command prompt. Type "wuauclt.exe /updatenow".
3. Go to Control Panel > Windows Update. Windows 10 should start re-downloading.
If all goes well, you won't have any issues when Windows 10 downloads again.