u盘装系统出现efi usb device has been blocked by the current security policy 怎么解决？

海淘来的y500，win8系统 想换win7 ，u盘装结果出现了efi usb device has been blocked by the current security policy。怎么办？坐等大神提供解决方案。

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你按F12，有两个DVD启动选择。不要选择EFI那个

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Bios禁止usb吧。。开了应该就可以。。还不行就再下一个系统

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