I think it's seeing the original SSD. You got the G750jx - DB - 71? If you did, it' should have two drives that came stock, one SSD and one HD at 5400 RPM. Mine is partitioned like your was, but the SSD was a 256 split into two drives. Did you try going to my computer and see what drives show up there? It should be 3 drives right now if you put the 500 gig SSD in place of the HD. If that's the case, then you are more than likely fine.
I just got a Samsun EVO 500 gig delivered from UPS about 20 minutes ago and will be swapping out drives tonight. I am still trying to decide if I want to leave the 256 as the second drive or the 1TB HD as the second one. I am going to clone my OS to the Samsung. So anyway, look at "my computer" and see how many drives are showing.