Sandisk Extreme 480GB SSD on Macbook Pro 15 inch mid 2012

Heres an update.  I went to the apple store last night and bought an adaptor for hard drives that run through the fire wire…when I plug the ssd in there, i can run it without a hitch.  The problem is when I connect it internally with the SATA cable.  The original hard drive still works internally.  I also was able to upgrade the firmware for the 480gb ssd.  Any ideas?  Thanks again in advance guys.  It is much appreciated!