Dear Philip,

I have done the following steps:

(a) Verified window version, it is confirmed OEM version.

(b) Used Neosmart and RWeverything to obtain the window product key. Both of them return the similar product key.

(c) Used MediaCreationTool and download the window 10 64 bit.

(d) run the window 10 setup exe in the pendrive, it prompt for window product key insertion, so I enter the key obtained earlier on in step b. It says that the key didn't work and couldn't get through.

May I know how may I solve this issue?

Btw, I am using window 8.1 Single Language.

Looking forward to hear from you again.

Thank you in advance.

So there is a problem with the Windows 10 TH2 Media Creation Tool. It automatically selects Windows 10 instead of Windows 10 Single Language for a Windows 8/8.1/10 Single Language base install.

It also does not show Single Language as an option if one unchecks the option to allow the tool to automatically make the selection.

Ironically if you change language and revert back to the original language then the Single Language option will show... see here:

https://www.youtube.com/watch?v=q8h5j_xNu2Y&feature=youtu.be  

The  Windows 10 TH2 Single Language Edition should automatically input and accept your Windows 8.1 Single Language product key.

How did your install go? I've been highlighting this issue in more detail here:

https://www.reddit.com/r/Windows10/comments/3x27eo/bug_windows_10_th2_media_creation_tool_single/