Using an old HDD as a secondary drive

Solution
So just to be clear:

Setup windows on new pc's ssd
Plug hard dive in and move files to ssd
Format orignal hdd
Move files back to hdd

If so then yes that will work.
As a secondary drive you correct in that you can access the data wihtout loosing anything.

It would be best to transfer that data someplace else temporarly and then format the old drive and transfer it back if it has an old windows installation on it.
You can delete out othe windows, program files and program data folders to clear space though if trasnfering the data is not an option.
 
Would keeping the data on the drive then installing it to my new pc and then transferring everything over to the ssd in the new pc then formatting it work?