Windows 10 is installed on SSD. It is recommended to prepare a recovery media (a set of DVDs), so if the hard drive fails, you would be able to boot from the DVD and either run diagnostics, or restore/recover the operating system and system files. HP has a utility to create the recovery media (included with the desktop); and Windows 10 has a couple of methods of its own to do the same (to create a bootable DVD or memory stick).