You can do it from the install disk of Windows 7. IF you want to completely wipe the entire drive using a low-level format procedure then go to this link below. It's easy to do and the time-consuming part is waiting for it to finish.
Be sure to
Use the Clean All Diskpart Command.
http://www.sevenforums.com/tutorials...t-command.html
After it's done you can continue on with the Windows 7 installation process. BE SURE you have downloaded all the particular Windows 7 drivers for the model of laptop you'll be installing it on prior to the install and store them on a thumb drive or CD-RW disc.