Cannot install Windows 7 because no boot device is recognized.
The BIOS setting disable CSM in default in order to install Windows 8. If you need to install Windows 7, please enter BIOS setting and go to [Boot] tab. Click [CSM parameters] and set [Launch CSM] to [Enable]. Save and exit, enter BIOS setting again after reboot, then you can set up [Hard Drive BBS Priorities] under [Boot] tab.