David, for this kind of behavior what we recommend customers to do is to check if they are running the latest BIOS available for the product. Download Center
Here are some BIOS versions that provided fixes related to USB
0077 Download Center
0064 Download Center
0051 Download Center
Please make sure you are using the following USB 3.0 driver Download Center
Are you getting the same behavior when you plug another device such as mouse, keyboard, another HD?
Could you please provide me the complete model number of the Seagate hard drive?
Hi Sylvia - the external seagate drive is samsung drive says model SRD0SD1
I do not have another USB 3 drive to test, but all my other devices, which are USB2 , including drives, do not cause the problem when plugged into the USB Ports (whether plugged into the USB 2 ports or USB 3 ports) . And when this device is plugged into a USB 2 port it does not cause a problem. And when this device is plugged into the USB 3 port AFTER the computer has booted, it does not cause the problem.
It is only when this device is plugged into a USB 3 port prior to boot, that the computer hangs on startup.
Well David, it looks like it is a compatibility issue with this hard drive. Could you please test the board out of the chassis just to discard any grounding issue?
This link will provide all tested peripherals on 6th series motherboards, but it does not show any USB device. Intel� 6 Series Chipset Boards — Tested peripherals
The only way to find out if it is something else, like a defective PCH, is testing another USB 3.0 device.
You can try with a USB 3.0 flash drive. If you got the same behavior, we can help you replacing the motherboard if it is still under warranty. Please get in touch with our Warranty Department so they can help you to replace the unit: http://www.intel.com/p/en_US/support/contactsupport