Hi
You need to get EasyBCD to remove Windows XP from the boot menu.
It's important to remove the Windows XP install from the other drive so that it's no longer in the boot menu, even if it's not set as the primary OS.
If you don't remove it from the boot menu and then delete the OS everything goes really bad.
EasyBCD is easy to use and free.
It should look like this when you get done with only Windows 10 shown in the boot list.
Link Removed
To migrate the OS to another hard drive you need some kind of migration software to do it easily.
There may be a free option but I use EaseUS Todo for my backup software, and it's very reliable.
Best free backup software for Windows 10/8.1/8/7/vista - EaseUS Todo Backup Free
You need the home version to do the disk transfer, but I see there's a trial version that you might be able to use once.
I use the free version to make system images of my C:\ drive in case of emergencies, I can't say that I've done the disk transfer thing myself.
I'd recommend that you install and use the free version, even if you don't want to buy the pay version to get the transfer capability.
This it kind of the thing I preach about but having a System Image file has saved me from hours of work many times over the years.
If everyone would make a system backup there would be a lot less posts on forums like this.
Mike