To bypass the activation window at the beginning of the installation, You can use a default/generic product key. You can use this key to continue however this key will NOT activate windows:
If you are going to download Windows 8.1 RTM on your computer, pay attention to this post. Here, MiniTool Partition Wizard shows you the detailed steps to download and install Windows 8.1 RTM after giving a brief introduction to it.
Download Windows 8 RTM - The Windows 8 RTM 90-day evaluation is designed specifically to help IT professionals test their software and hardware on the final version of Windows 8...