If you haven't heard, those who purchased a new Mac with Apple's built-to-order 3TB hard drive option found themselves unable to utilize Boot Camp assistant to install Windows. Boot Camp Assistant is currently limited to drives up to 2.2TB. Apple hinted that support might come at a later date, but TwoCanoes shares a step-by-step guide for getting the job done in Boot Camp until then:
Since it is not possible to get around the 2.2 TB limitation with booting Windows, it is possible to organize the partitions so that Windows is the last of the first four partitons and is within the first 2.2 TBs of space on the drive. Since the Mac can see the remaining space above the 2.2 TB limit, this space can be used for addtional storage space for OS X.
In order for Windows to boot successfully and still be able to utilize all of the available space on a 3 TB (or larger) hard drive, Windows must be installed on the fourth partition. You can use Disk Utility to create the partition, but since Disk Utility does not show hidden partitions, it can be difficult to see what is going on if some partitions are hidden. To have Disk Utility show hidden partitions, open Terminal and run the following command: