Every laptop manufacturer provides different methods for resetting the laptop to factory defaults, some have a recovery partition and you can use a key combination at boot time (Alt +F10, Alt + F11) to evoke the recovery process, while others provide recovery media in the form of CDs or DVD.
If for some reason, neither of these options are available to you or the process fails you will need to contact the laptop manufacturer and see if they will ship you new recovery media most will for a slight fee (to cover shipping and handling), or else you will need to obtain Windows 7 installation media that corresponds with the COA (Certificate of Authenticity) sticker on the bottom of your laptop in-order to perform an install. I believe these resources here
Download Windows 7 Integrated With SP1 ISO – Official Direct Download Links are still available and may help, but my first call would be to the manufacturer as their resources will be specific to your particular computer.
Regards
Randy