Hello Madhur B -
The illustration shows an entry for “Previous Windows Installation.” Unfortunately, my Vista does not have that entry in Disk Cleanup.
1. Can’t I merely delete the folder from Windows Explorer?
2. Also, you suggested to back up that folder. Because of its size it would require an external hard drive. Assuming I would do that, I really do not want to. One of the reasons I want to delete that folder is when I do a virus scan, Windows.old is scanned on all my drives and it takes too long.