2 (3) possibilities off the top of my head:
1. Drivers to hotswap the CD drive were not installed, so the OS did not recognize it as a removable device when she got the computer
2. Windows updates installed since she got the computer alter the way its listed in device manager
3. It wasn't actually listed under hard disk drives (or how its displayed depends on the media in the drive, dunno, never paid very close attention)
Is there some other problem you are looking to resolve with the drive, or is it just a question about why its displayed differently?
If there really is a difference, it's probably due to a difference between drivers before compared to now, or differences in the OS from windows updates.