How do I clean an infected Windows 8 notebook

My husband’s Windows 8 laptop is severely infected with malware and viruses…

I don’t like or use Windows 8 so I need some information on how to clean this computer.

Will doing a factory restore of the laptop clear it of the viruses or is there another way.

Also, once it is cleaned, what ‘free’ antivirus/malware software is available for Win.8?

I can clean a Win.7 computer but as I said before I stay away from Win.8 so any advice would be greatly appreciated.