Disk Cleanup has probably always worked this way, but I have been having fits figuring out how to get rid of Windows.old, which contains the previous operating system and files from my Vista implementation. I got some things I needed from the .old directory, but administratively it is very difficult to delete.
Disk Cleanup a utility that comes with the operating system works. I got the directions from How to Delete and Remove the Windows.old Folder. Here are the instructions:
Step by step use of Disk Cleanup to Remove Windows.old Folder
Click on the Start button on the task bar for our task to windows.old removal.
Follow the "All Programs - Accessories - System Tools" path on the Start menu.
Click and select "Disk Cleanup".
When the Disk Cleanup Options dialog screen is displayed select Files from all users on this computer option.
Select the hard disk Drive where the Windows.old folder resides.
The Disk Cleanup utility will scan the driver for not used and unnecessary files.
When the scan is completed check the "Previous Windows installations".
When the wizard requests your confirm to delete the Windows.old folder and its content files, select Delete.