How do I delete windows.old in Windows 7?

Click on Start/All Programs/Accessories/System Tools/ Disk Cleanup.

Once the dialog box comes up, select the drive that has the .old and click Okay. The system then scans for the files to be cleaned up and another dialog box opens with the selection.

Click on the button labeled "Clean up system files" at the bottom of the dialog box.

Another dialog box will come up, select the drive again that has the .old files on it. The system will perform another scan for the system files that need to be cleaned up.

After scanning, another dialog box opens up and there you will find a list of check boxes. Scroll through and check on the box labeled Older versions of Windows and click OK .

*This represents a change from earlier versions that allowed this in Disk Clean up without the extra steps.