It needs to be formatted as a GPT drive. It's probably formatted as a MBR drive at the moment. Go into control panel, administrative tools, disk management, and find the 3TB drive listed there. Right click on it, and if the drive only has one partition and is empty, there will be an option to convert the drive to GPT. It HAS to be empty and only have one partition for this option to present itself. If it's not empty, move anything off of it to another drive, make sure there's only one partition listed on it, format the drive, and the option should be there