Delete windows.old folder by Disk Cleanup

I've upgraded to windows 7 RC from the beta . And I found that a windows.old folder created.
Inside the folder i was able to delete all the files, but I am not able to delete the windows.old folder.It get a message "You require permission from administrators to make changes to this file".

But I'm an administrator and had all possible rights and ownership of the folder.How can I delete this folder?

You can use Disk Cleanup . The Disk Cleanup exe file is located at C:WindowsSystem32cleanmgr.exe.
You can check the Files discarded by Windows upgrade option to remove the Windows.old folder.
Issue solved.