I'm still confused by this.
Select any file you want, right click it and select properties. Under the General tab click the ‘Advanced’ box. Uncheck the option for file compression. Click OK and then Apply. a page will appear giving you the option to apply this change to just this folder or to all folders.
I've tried this but I see no option for 'all folders', only individual files.
And my main drive - Properties, General, - the Compress Drive to Save Disc Space is unticked. I've changed nothing that I know of and this 'compression' malarkey appears to have started of its own accord.