The 0x800f0805 error is one of the common activation errors. This usually happens when you are trying to upgrade from Windows 10 Home to Windows 10 Pro.

What is the reason for 0x800f0805?

Not to be mistaken with the other common error 0xC004f050. This error code indicates that your copy of Windows has passed beyond the trial period. Hence, no matter which product key you enter, it will never activate your computer.

In order to fix this issue, we must simply ‘re-arm’ Windows. Meaning, to restart the trial period.

Here’s how to fix 0x800f0805:

1. Make sure that your computer is updated.

Go to Windows Updates, and check for updates. Get everything installed properly. If this is not possible, proceed to the next step.

2. Enter Command Prompt

Go to the start menu > type in ‘cmd’ > Right Click on the Command Prompt and open it as an Administrator.

Important: You must run command prompt as ad administrator, otherwise this will not work.

Type in or copy and paste this command:

slmgr /rearm

Press Enter. If you have done this correctly your computer will ask you to restart Windows.

That’s it. We hope that wasn’t too hard, there’s only two steps anyway. If you still need help, do not hesitate to contact our technical team at anytime.