Darik's Boot and Nuke, or most drive manufactuer's tools will do this. They run under DOS not Windows 7, but will come on a boot disk. As a precaughtion disconnect any good drives, DBAN will nuke the lot if you're careless.
Download the ultimate boot CD, it included both of the above and loads of other handy stuff.
EDIT: You don't do this in device manager, you should do it in Computer Management (or what ever W7 has), there's a section called disk management.