Getting a new laptop, need to replace harddrives.

I'm getting a Dell Inspiron 7559 with initially nothing but a 256GB SSD which has a Windows 10 pre-installed. It will have a slot left for a hard drive and I plan to put in the one I currently have in my laptop which has Windows 7 installed. When I put it in will Windows 7 also work cause I'd rather that not happen since I Just need this one for the space. Is there any way around this?