Are you still on windows 7, or has installation and upgrade to windows 10 happened? Which is the case will have a very strong effect on what you must do next.
If you're still on windows 7 I suggest disconnecting from the internet, running the commands britechguy suggests then if they say everything is OK go to windows update and set it to "check automatically but ask me whether I want to download and install", then hide KB3035583, then uninstall KB2976978, and all the other GWX related updates(see below).
After doing this you'll need to in future visit "windows update" in control panel every tuesday evening/wednesday morning to accept all "Security Update for..." and reject all other updates, however even this advice isn't foolproof any more, there has been a Security Update to IE which carried GWX like stuff(KB3146449) and I'm still investigating if the latest update to IE still has this nasty inside it.
You can also create registry keys which block upgrade and black GWX, hopefully. The explanation for that is also listed below. GWX control panel can be a helpful program to use alongside these other methods.
You should also look for a folder on your C drive called $WINDOWS.~BT . If it is there, make sure hidden files are showing so you ca see if it is, then delete it if you can. If not try using disk cleanup to do this, if that doesn't work either you'll have to modify permissions and ownership of that folder so you can delete it. You may also need to modify permissions and ownership if you find any instances of gwx.exe remaining on your system after you've removed the updates discussed below, but don't do any of this permissions/ownership changing until AFTER removing the updates themselves the normal way.http://www.bleepingcomputer.com/forums/t/551980/the-windows-updates-monitoring-thread/
(this lists all the updates for the last few years, but it isn't so easy to find from it a list of ones to avoid because it's done in date order)http://forum.notebookreview.com/threads/windows7-8-updates-to-hide-to-prevent-windows-10-upgrade-disable-telemetry.780476/
(there is a list here, you have to scroll down a long way though. The above might not be relevant but may be helpful. It also discusses other methods but these may be trickier to do, registry editing and script running can go VERY badly from even tiny errors, if in doubt ask for further advice.)http://www.bleepingcomputer.com/forums/t/599235/for-those-that-wish-to-stay-with-7/#entry3887720
(Make sure these are removed too)http://www.bleepingcomputer.com/forums/t/611229/windows-7-updates-unsafe/#entry3980053
(and remove these)http://blog.ultimateoutsider.com/2015/08/using-gwx-stopper-to-permanently-remove.html
more info below, but it's old so not as complete as some of the advice abovehttp://www.howtogeek.com/228551/how-to-stop-windows-7-or-8-from-downloading-windows-10-automatically/?PageSpeed=noscript
Edited by rp88, 15 April 2016 - 12:07 PM.
Back on this site, for a while anyway, been so busy the last year.
My systems:2 laptops, intel i3 processors, windows 8.1 installed on the hard-drive and linux mint 17.3 MATE installed to USB