Again as I have been saying in other threads why not just use a usb external and save your optical drive. I have Windows 7 installed on a 500gb Seagate which I run on my Windows 10 laptop and it works like a charm.
I have several portable USB HDDs. But Usb is slower than internal, AND, I'm trying to use an SSD as my internal drive, for the speed benefit. I can't afford a good sized SSD for the laptop, so this may be a good idea for my needs.
The laptop in question is a brand new Dell with a 1 TB HDD, which I would put in the optical drive caddy for the extra storage. Having to lug an external drive around is a hassle to me, kinda takes away from the "portableness" of the laptop.
A laptop should be self contained. And I never play cds or dvds in it. I really have very little need for the optical drive. But IF I ever did, I have an external optical disc drive for that.
But then, I could give some thought to using the 1 TB HDD out of the lappy as an external instead, if just for storage. I don't really intend to dual boot or anything.