My Dell Inspiron N5110 came without any operating system. I installed Windows 7 myself using my own copy.
In the disk management, it shows two hidden drives. One is ~40 MB labeled OEM partition (100% free) and the other is OS partition (99% free). Since my laptop never had any OS or backups to begin with, I want to delete those partitions to make some other partitions. The disk management is not able to edit or delete those drives.