Windows 7: Unknown "Group or user names" in Folder Security Tab

Greetings!

Yesterday I noticed an Unknown User/Account in one of my D:\ Folders which I managed to solve but since this isn't the first time this has happened I'm looking for a different approach to solve this issue.

So far I'm suspecting this User/Account to be something from an older Windows 7 Installation since when formatting my PC I'll only whipe Drive C:\ running the Windows Installation but not the other ones like D:\ housing Games, Programs and the like.

Question:
Is it possible to get a "clean installation" of Users/Accounts by copying the files and folders to a second HDD, format the first one and then move the files and folders back to the first one or will the faulty group and user names just move along during the copy process?

The 2 Attachments show 2 Folders on the same HDD displaying partially different Group or user names which kinda irritates me...