a.trkaleski :
I currently have Windows 10 Pro, I made a bootable USB also.
I currently have a Sata I 1 TB installed, And I bought a new one (Sata III 2TB) 3 Hours ago. They are not the same brand tho.
Desktop
My Old HDD is dying and its very slow (Sector problems, and some other things i dont know)
I also have a back up of the important files I need on an external drive so I dont mind losing what I have on the old one, but if its possibly I want to keep the D: Disk
A clean install on the new drive is recommended here.
Disconnect all other drives, and install on this new one.
How to do a CLEAN installation of Windows 10
Later, reconnect the old drive, retrieve whatever you want from it (if you can), and then wipe the entire drive. All partitions.
Given "sector issues", I wouldn't use it for anything critical.