I think you cant install it on there, check the Erase tab, if you can erase that partition from there but I think it wont be available, I think only HFS+ partitions types are valid for that, not free space.
Typically you need to create an HFS+ partition type, not an emtpy partition type, you can do that with windows I think but I dont know the exact details. You can do it with third party partition managers like Parted Magic (you can create HFS+ partitions straight) or Acronis Disk Director (you can create custom partition types, you need to create one type 0xAF IIRC, it will show as a weird name, but as long as its 0xAF type its alright).