Refer to your user manual if you want to return the laptop to factory
condition. If you don't have a user manual, look on Packard Bell's
website for one or speak to their tech support.
If you are not trying to return the machine to factory condition,
normally you format a hard drive during the installation of another
operating system (boot from that operating system's CD/DVD disk) or use
a disk formatting utility such as the one that comes with Acronis Drive
Director or a utility that comes from the hard drive mftr.