GWX Control Panel (previously named GWX Stopper) is a free program that you can use to do the following on Windows 7 and Windows 8:
• Remove the "Get Windows 10" icon that appears in your notification area.
• Prevent your Windows Update control panel from upgrading your computer to Windows 10.
• Prevent your computer from secretly downloading Windows 10 installation files.
• Detect and remove the hidden Windows 10 installation files if they're already on your PC.
UPDATE (November 1, 2015): Due to popular demand, version 1.5 of the program now includes the ability to delete the hidden Windows 10 installation folders (Windows.~BT and Windows.~WS). There are a few other features intended to improve the user experience and assist tech support staff who use GWX Control Panel to remotely help customers. There was a LOT of under-the-hood work done in this release- please let me know in the comments or on the Ultimate Outsider Facebook page if you see unexpected behavior.
https://archive.is/9bDA9
http://blog.ultimateoutsider.com/2015/08/using-gwx-stopper-to-permanently-remove.html
Here is the original download link:
http://ultimateoutsider.com/downloads/GWX_control_panel.exe
Here are some mirrors:
http://upstore.net/EBvMcmi
http://www.fast-files.com/getfile.aspx?file=101308
http://www.mediafire.com/download/65c9vmaeirnfivz/GWX_control_panel.exe