Ele diz no meio :
Moreover, the CentOS 7 installer image has a special partitioning which, as of July 2014, most Windows tools do NOT transfer correctly leading to undefined behaviour when booting from the USB key. Applications known (so far) to NOT work are unetbootin and "universal usb installler". Confirmed as functioning correctly are Win32 Disk Imager and Rawrite32 and dd for Windows.
Portanto, basta usar a ferramenta Win32 Disk Imager , com as imagens fornecidas.
iso2usb e Pendrivelinux.com são outras opções.