Windows 10 was launched not long ago and since it's offered as a free update for those on Windows 7 and 8.1, it's nothing unexpected that such a large number of individuals hurry to introduce it.
Some, be that as it may, are getting different lapses and one shows the Windows Update Installation Failure error code 80240020 logged under Windows Update History.
Essentially, this happens when you attempt to upgrade Windows 8.1 to Windows 10 utilizing the implicit Windows Update highlight and as per client reports, this mistake is shown once the download arrives at an end.
How to Solve Windows 10 Update Installation Failure Error-
At the end of the day, there's nothing the matter with the update, so you need to hold up a couple of more days until Microsoft really makes it accessible for your PC. Else you can try below trick to resolve such issue.
Here is a basic approach to alter this sort of mistake, empower the upgrade regardless of the slip and it includes changing a registry key. So open your registry by writing "regedit" (without quote) in the Start screen and go to the following path-
In the event that the key does not exist, create it manually, but rather verify you take after the accurate way we said above.
When you are there, you have to right snap in the right half of the screen and make another DWORD (32-bit) quality called "AllowOSUpgrade" clearly without the quote. In the quality field, enter "0x00000001" and that is it.
Reboot your PC, backtrack to Windows Update and check for new updates. Once the Window 10 upgrade is accurately recognized, you should able to click on tab "Get Started", Microsoft clarifies, which essentially dispatches the update process and gives you a chance to introduce Windows 10.