[SOLVED] windows 10 in 2 hard drives

[TeriyakiShak]

Recently I rebuilt my computer which included getting a new motherboard. I used the windows installation media from a backup hard drive and installed Windows 10 on a brand new hard drive. I read a guide that was brought up multiple times from previous threads which I followed. It emphasized unplugging any other hard drives which I did, but one of those had the Windows 10 I used with the old computer.
So my question is What do I do with the old windows 10 files? I'm not sure if I should delete them because I don't even know what they are. Also, I'm not sure if there's important info attached to it that I might need later. Can anyone tell me if it's okay to delete the windows 10 files on the older hard drive, and also what the folders are?

 

[USAFRet]

You should find whatever critical personal data is on that drive, copy it to elsewhere, and then wipe that drive completely. All partitions.
Then, use it as desired.

 

[TeriyakiShak]

You should find whatever critical personal data is on that drive, copy it to elsewhere, and then wipe that drive completely. All partitions.
Then, use it as desired.

Okay I'll go through it real slow