Recovered Files Are All Zeros

I just received the latest windows update.  A notification popped up asking to delete the previous version of windows to free up disk space and I agreed.  I had no idea how much non-system information was part of "the old windows" so many important files were deleted.  I have tried nine different types of recovery software, and they all can find the files, say they are not overwritten with anything, but recover only a file full of zeros.  I confirmed it is full of zeros by opening it in a hex editor, notepad++, the native file-type client, and the preview editor for each recovery software that had one.  I have tested by deleting some files that I've had for a while but don't care about.  Some of these are not found at all, while others are also recovered as zeros.  Why is this behavior happening and how can I recover my files?