dual boot - Install Ubuntu 14.04 / 15 in computer with Windows 8.1 Legacy installed before

I want to install Ubuntu 14.04 to dual boot with Win 8.1 installed before.
I installed Windows 8.1 in Legacy mode, my laptop is Dell Vostro 2420 which support UEFI but I disable UEFI boot mode before install Windows. Now, when I create Ubuntu 14.04 installation in my usb by Linux Pen Drive, it's UEFI certainly which I can't change. Can I install Ubuntu in Legacy mode and how?