I'm unable to boot my Windows 10 installer USB in UEFI mode?
Two important points:
1: The Windows 7 USB/DVD Download Tool is not compatible with USB 3.0. To create a USB stick that is compatible with USB 3.0 using the native boot experience of the Windows 10 Technical Preview media (or Windows 8/Windows 8.1), use DiskPart to format the USB stick and set the partition to active, then copy all of the files from inside the ISO to the USB stick.
2: UEFI (CSM disabled) requires the USB stick to be formatted FAT32. If your stick is formatted NTFS, it would explain the behavior you have described.
You will be able to boot in by using Rufus.
- Prepare the usb device in Rufus. Select GPT for UEFI only. Select FAT32. UEFI specs define FAT32 as mandatory. (Source)
- Set your bios to default settings. (This enables all uefi options and secure boot)
You can now install windows 10 in uefi mode.