To reset your device to the default factory settings you need to use recovery media which can be found here:
Lenovo: Windows recovery media for Lenovo laptops and the X1 Tablet bought before autumn 2016 can be downloaded via Neptun Software Service. There is also the possibility to order recovery DVDs via Tel. 0800 55 54 54 (cost of handling and shipping will be charged). Newer device models can create a Lenovo Recovery USB key via Lenovo Digital Download Recovery Service (DDRS).
HP: Windows recovery media for HP laptops can be ordered using the support chat or via +41 44 200 41 21.
Mac OS X: Software via App Store or new installation via recovery partition.