iirc, Acer machines all have the OS install files stored on the hard disk rather than on a CD. And I think they are also configured to create a virtual partition on startup. This may simply be the way it holds these OS installation files separate from the C drive, storing it as a disc image, so it can be mounted as though it is a CD. But I might be wrong.
So on that assumption, I think the question you need to answer is do you want the OS install files on the hard disk? To answer that question:
1. Can you afford to delete them? Do you have an install CD?
2. Is the machines cheaply made? Because if the cd/dvd drive has internal usb connectivity, that will probably render the cd/dvd drive useless without an OS installed, meaning that you can't install an OS from CD, and you can only install one from the disc image on the hard disk.