I had 25 GB of free space. I tried to install windows 8 and it went till setting of files and settings and then it crashed. Now I only have 10 GB of free space and when I run the installer, it says to free up at least 20 GB. I do not understand where my space went.
I checked under %localappdata%\Microsoft\WebSetup\. It only stored the installation files and deleting it freed only 4 GB.