Can't Boot PreInstalled OEM Windows 8 From External Hard

Hi, I have a lenovo y50 laptop that comes preinstalled with windows 8. The laptop has a 1 TB hard disk that I decided to replace with a SSD. I then installed windows 7 on the SSD and the SSD became the internal storage and the 1TB hard disk became an external storage connected through the USB. I use legacy boot to boot windows 7 from the SDD and it works great. My problem is I can't boot...