What I did when I had a Gigabyte mobo was to move the boot drive onto the Gigabyte SATA port, make sure this is running in the same SATA mode as the Intel. Then boot up and check that it boots. If it boots then shutdown, change the Intel SATA port mode to RAID, boot up and install the required drivers. Give the system a reboot to make sure everything is OK, then shutdown and move the boot drive back to the original port and hopefully it should boot up.