If the current drive is still good there are different methods for data recovery. But if the drive has failed for some reason like bad heads then you would need to bring it in or send it out to a professional service that specializes in data recovery.
A spare drive allows for copy + pasting files and folders or for using a data recovery software even one for cloning an entire partition from one drive to another. A free drive partitioning tool known as GParted live for cd also has the option for copying entire partitions from drive to drive as well. All this depends on whether the drive is still in working shape.
You may only need something simple like replacing the data cable or repair to the boot sector if the drive is still good in order to see the system running again. On older system with an ide drive the grey colored flat ribbon type cables tend to get hardened up and no longer usable from age. Some information like the operating system Windows and system information would be usefull since there are different methods for the different versions of Windows and other operating systems.