I am trying to dual boot windows 7 (3TB hard drive) and Ubuntu 14.04 (1TB hard drive). I already have windows installed and am trying to install Ubuntu, however, the option to install Ubuntu alongside Windows 7 is not shown. This may have to do with the GPT partition table I am using for windows, since I am using a 3TB hard drive. Is there a way to get Ubuntu to recognize a GPT partition table?
If you've got two separate hard disks, I recommend using the "Something Else" partitioning option; I'm not sure if the more automatic options will work with multiple disks. Besides, you know where you want things to go, and the installer doesn't.
Ubuntu has long supported GPT; that's not an issue. You should be wary, though, of boot modes. If Windows is installed to a GPT disk, it must be booting in EFI mode. If you install Ubuntu in BIOS/CSM/legacy mode, that will create complications. See my page on EFI-mode Linux installations, this Ubuntu documentation page, or this askubuntu question about installing Ubuntu and Windows 8. You shouldn't need to do anything special because of your second disk, aside from using the "Something Else" partitioning option.