Format disk with one Windows and one Mac partition
If you have 2 hard drives you can do this way:
1) On 1st drive install osx. Then use bootcamp assistant to re-partition the disk 1 and install windows on second partition. At this point you can via disk utility format the second drive as you wish (e.g.: second drive 1Tb= 500gb fat/ntfs for win data and 500gb hfs+ for osx data);
2) On 1st drive install osx. Then use bootcamp assistant and select secondary hd (not the osx' one) and install windows. Now you have dual boot on 2 separate disk, 1 fully dedicated to osx and one to windows.