I have a Sony Vaio Fit laptop. It is my main working (and only btw ) laptop. So I thought I'd just dual boot Windows 10 with 8.1. So, I created a 40GB partition on my hard drive. I downloaded the x64 version of Windows 10 and burned it to a USB drive with Windows 7 DVD USB tool installer. I changed the BIOS settings such as boot from external drive 'enabled' and put that option on top of the list. Disabled the secure boot as well. And when I select boot from USB option, it says booting from external device failed, that is when the boot mode is selected as UEFI in BIOS settings. When I change it to Legacy mode, I'm able to get past the Install now screen and the choose upgrade or custom installation. But when I choose custom installation, and I'm allowed to choose a drive on which I want to install the preview and when I select the drive I have created, it says, Windows can't be installed because the selected disk is of GPT partition type, or something like this. What am I doing wrong? Please, someone help me out. Thanks.