Hi, I got my new Retina Macbook Pro 13, but with only 128 GB SSD. So I decided to put Windows 8.1 on a 64 GB SDXC card (PNY StorEdge) . I don't need Windows very often, so the speed is ok for me. The thing is, to have a full working Windows 8.1 to go, you need to format the SDXC Card using NTFS. But then the rMBP doesn't see the SDXC Card as a boot device (pressing ALT during boot). Only if I format the SDXC Card with exfat or FAT32, then I can see the SDXC card during boot. The problem is, that Windows 8.1 does not install correctly or does not boot from FAT32 or exfat. If I insert the SDXC card (using VHD and NTFS), I can boot Windows 8.1 on my DELL notebook without any issue, so the card is fine. How can I tell my rMBP to boot from an external NTFS drive? Thanks!