How do I restore my Hard Drives to factory settings?

Alright so I have 2 hard drives, a Samsung Spinpoint 320GB 7200RPM and a WD Caviar Black 250GB. I have installed Windows 7 on each of them many times, and over time this has caused a few screwed up partitions to appear that I can not get rid of and I am unable to boot from one of them. I want to know if there is a way to completely restore my hard drive to factory settings. By this I mean remove all of the operating system, the master boot records, everything. I want my drives to be COMPLETELY empty.