Ajeet, there is no safe way of recovering a BIOS password you have to remove the CMOS battery for several minutes to reset it back to factory.. This thread is about recovering the product key for Windows 10. If the OS was installed at factory then it will not have a product key as it is associated with the hardware. Simply reinstall it without the product key and it should auto-magically activate by itself. Best to contact your computer's manufacturer for advice on that.