Windows 10: can't opt out of insider program

My system is accumulating over a couple hundred gigs of data every single day..all in temp files..and my disk usage is always stuck on 100%..with apparently most of the resources being dedicated to compiling the useless things.
This means my system now runs like a pig in a poke. It takes 15 mins just to boot up, and I'm constantly having to use 3rd party programs to clear the absolute junk accumulating in the temp files.
I've spent hours looking for solutions, and seem to have narrowed the issue down to microsoft taking over my system so it can find out apparently everything happening on my system because I'm in the insider program.
I opted in to the insider build program some time ago, and now I can't opt out of it.
All the relevant options are greyed out.
As a last resort, I decided to simply reinstall windows using the installation media tool. So I spent the best part of an hour staring at the screen, only for the program to tell me without a hint of irony that 'Your system can't run windows 10'.
A ridiculous situation.
I haven't got the time, energy or the spare hard drive space to save all my data so I can reformat my drive and start again..and am considering a linux setup just to escape this win 10 nightmare.
Can someone give me some help? I just want to opt out of the insider program so I can get my property back to the state it was in almost a year ago.
I've looked thru the answers given to similar problems on here, and none of them have worked for me.

:)

 

opting out of windows insider program

Hello Scott, you are able to opt out of the Windows Insider Program by following the steps listed in the following link:

https://support.microsoft.com/en-us/help/10584/...

Hope this helps, and let me know if you have further questions!

 

insider program opt out

how to opt our of insider program

 

Opt out of Windows Insider Program to a Windows 10

Pick one:

• I want to opt out of the Windows Insider program & keep running Windows 10.
  
• I want to opt out of the Windows Insider program, go back to Windows 7 & then upgrade to the current public build of Windows 10.

Does this concern the same computer as in your previous thread? =>
http://answers.microsoft.com/en-us/windows/forum/windows_10-performance/windows-10-after-upgrade-issue/af1e3f89-d399-4152-b4cb-d9af70b285e3