Duplicating a disk

If you have two IDE drives that are of identical size, and provided that you are sure they contain no bad sectors and provided neither are mounted, you can run

dd if=/dev/hdc of=/dev/hdd

to copy the entire disk and avoid having to install an operating system from scratch. It doesn't matter what is on the original (Windows, LINUX, or whatever) since each sector is identically duplicated; the new system will work perfectly.