Windows 7: Setup was unable to create a system partition or locate an existing partition.
Over the past week, I've installed Windows 7 and OS X more times than I can count. In attempting to figure out the easiest way to dual boot Windows 7 and OS X, I've also partitioned my drive a good 30+ times. So.. after messing up with an EFI bootloader, I was suddenly unable to re-install Windows 7. I encountered the error: Setup was unable to create a system partition or locate an existing partition. I also ran into the error: Windows cannot be installed on disk 0 partition 1.
I used Gparted to repartition my drive, and even used Disk Utility but repeatedly encountered the above errors.
As it turns out, I had another System disk attached (OS X on a USB drive) to my laptop and once I unplugged it, I was able to successfully install Windows 7.