As you should have understood from the beginning, you remove your entire operating system when you format C. This means that when you restart your computer and attempt to boot from your hard drive, it will not work because there's no longer anything there.
Ihe dị mkpa: Dị ka ị ga-aghọta site na mmalite, ị na-ewepu usoro sistemụ gị mgbe ị na-eto eto C. Nke a pụtara na mgbe ị malitegharịrị kọmputa gị ma nwaa ịkwalite site na draịvụ ike gị, ọ gaghị arụ ọrụ n'ihi na ọ dịghịzi ihe ọ bụla n'ebe ahụ ibu.