Do you want to restore the operating system? If so, there should be a recovery partition on it that you can access at boot up by hitting f5 or whatever it is for your model. If CD/DVD's came with it, boot from the OS disk and you should be good to go. If you want to recover say documents, photos, etc..., you are probably out of luck if it has been reformatted.
u can google for software recovery program, but depending on how the format was done most likely ur going to be out of luck. there is some software out there that trys scaning the media for informantion but most wont work because a format erases the file storage data tables. sorry