Reinstall Cubase on the new PC, and copy the files from your old computer, or insert the old drive into a spare bay as you suggest, or for people who lack a spare bay, you can buy an external USB disk drive CASE that will accept your old disk, and get your data from your old computer into the new one that way.
Remember that spinning disks have a limited life so GET YOUR DATA OFF YOUR OLD HARD DISK before that happens. I am saying this because my 2010 era disk just stopped powering up, and I hadn’t recently made a backup, and so after preaching backup to the other people, I am slain by my own sword, hoisted on my own petard. Learn from me, oh wise ones, and do better.
Will windows 10 have weird issues? Yes, and if not, just wait two weeks for the next crazy set of updates that breaks everything. Will windows 7 have issues? Yes, and they will probably never get fixed. Welcome to life on windows. (I do DAW stuff on macs and on windows, and frankly, windows sucks for DAW/audio-production work.)
W