I've installed Windows 8.1 to my Macbook Pro 15 mid 2012 via legacy mode, all went ok. It was installed to disk1s1 (HDD in optical bay), my OS X 10.11 sits in my SSD (disk0) on the main bay. Disk1s2 is a data partition. I can see the Windows drive if I press alt during EFI boot, but when I try to boot it, says: My HDD is MBR and my SSD is GPT. Code: /dev/disk0 (internal, physical): #: TYPE NAME SIZE IDENTIFIER 0: GUID_partition_scheme *250.1 GB disk0 1: EFI EFI 209.7 MB disk0s1 2: Apple_CoreStorage Macintosh SSD 249.2 GB disk0s2 3: Apple_Boot Recovery HD 650.0 MB disk0s3 /dev/disk1 (internal, physical): #: TYPE NAME SIZE IDENTIFIER 0: FDisk_partition_scheme *500.1 GB disk1 1: Windows_NTFS Untitled 128.0 GB disk1s1 2: Apple_HFS FCBD 372.1 GB disk1s2 /dev/disk2 (internal, virtual): #: TYPE NAME SIZE IDENTIFIER 0: Apple_HFS Macintosh SSD +248.8 GB disk2 If I remove my SSD, Windows boots normally and I can work all day. How to boot with both drives connected?