I am going to show appalling ignorance.

I run Win 7 Ultimate SP1. I have not "updated" to Win 10, but probably eventually will want to.

I have a second, spare hard drive (500 GB) installed in this PC but it is totally unused (Healthy, Primary partition.).

I assume installing Win 10 on the hard drive containing my present installation of Win 7 and all personal files, programs, etc will wipe everything. Is that correct?

How would I go about installing Win 10 on that drive? Should I use that drive?

Or should I use the unused, spare hard drive?

Would someone be willing to explain the plus and minus of the two alternatives? And then walk me through the procedure ? Or direct me to a good reference?

For example can I transfer my personal data (from a backup) to the Win 10 drive whichever drive I use for its installation? I gather I must install all programs again in either case. Is that correct?