Remove Windows.old after using in-place upgrade method on Windows Server 2012 R2 Preview

After obtaining Windows Server 2012 R2 Preview, I thought of upgrading my lab environment. Upon completing Server 2012 R2 Preview upgrade, I noticed that there’s a Windows.old folder in my System drive which takes around 20GB of space. now that I have already upgraded in to Server 2012 R2 Preview and confirmed that all my applications / file are available, I decided to delete Windows.old folder. Best way to do this, is to use Disk Cleanup Tool.