Installing a different version of Windows to 2 different drives

I have recently purchased a brand new DELL Inspiron 15 (5559) laptop with Windows 10 prenstalled on the computer. I still haven’t powered on this computer.
I also have a windows 7 ultimate 64 bit (Service pack 1) retail CD and a brand new Samsung SSD that I’ve purchased recently.
I would like to keep the old HDD with preinstalled Windows 10 and to install Windows 7 to the new SSD. Can I just replace the original HDD with the brand new never used SSD and clean install the Windows 7. The reason I ask this is because I would like to keep the original HDD with Windows 10 preinstalled in case I’ll change my mind later and want to use that one.
In other words can I have 2 different HDD with 2 different Windows OS that could be swapped in a single laptop if needed?
All required drivers are available for download on the Dell web site because as this PC comes with Windows 7, 8.1 and 10 (64 bit).

Thank you for your help!

There is no problem to keep the old HDD with installed Windows 10 and to install Windows 7 to the new SSD.
As it is a Skylake CPU you probably will have problem to install Win 7 as it doesn't have USB 3.0 drivers (no mouse).
If you do have a CD / DVD ODD, you can install, but isn't easy. When you finish you won't have mouse and wont be able to use the USB port to install the drivers needed.
I've made a tutorial to install all needed drivers to the Win 7 installation disk.
Create a Windows 7 USB flash installation with new drives for new MB's

Welcome to the forum there is no problem with doing that don't turn it on swap drive boot seven and your good to go make sure you get network drivers first or you won't be able to download drivers

Thank you so much for your advice guys. I’ll try to install Windows 7 over the weekend using the posted manual and the original USB 3.0 drivers from Dell’s website.