A time ago to a PC without optical drive installation CentOS7 (CENTOS-7.0-1406-X86_64-DVD.ISO), the formula directly with the Universal-usb-installer directly to the flash drive, the smooth start, but unable to install, The prompt did not find the installation media, after the experiment, found that using CENTOS-LIVECD instead is able to successfully enter the demo system and installation.
Then check the documentation and find the answer in the CentOS WiKi (http://wiki.centos.org/HowTos/InstallFromUSBkey):
7 as the Do from " Universal USB Installler " as for Windows.
The approximate meaning is as follows:
Starting with CentOS 7, the installation image has a special partition that may cause most Windows tools not to be converted correctly to a bootable USB flash drive. Currently known not to work correctly includes, "Universal-usb-installer". Identify the "Win32 Disk Imager", "Rawrite32", and "DD for Windows" that work correctly.
OK, download Win32 Disk Imager 0.9.5 version, select the image and USB drive, then install it successfully.
CentOS7 How to install with USB flash drive