Upgraded to Windows 10 about a month ago. Why is my C drive named Windows8_OS (C:)?

[Windows Central Question]

Upgraded to Windows 10 about a month ago. A previous installation of GameMaker Studio stores files in a location I cannot find in my file structure. While looking for them, I noticed that my C drive is named Windows8_OS (C, and there is a folder named Windows.old as well.
Is this normal? Do I still have Windows 8.1 installed on my computer? Does it have to be there, or can I delete it?

 

[realwarder]

You can rename the drive to anything (right click on the drive and select Rename)

Safest way to remove Windows.old folder is to use the Disk Cleanup tool. Select Cleanup System Files/Previous Windows Installations.