On a fresh install two virtual USB devices are installed, virtual floppy and virtual CD-ROM. Why are these installed and how do you use them?

These are most likely the virtual media features of the Dell Remote Access Card (DRAC) that is installed in the system. During boot-up you can press CTRL-E when prompted to be able to set the IP address of the DRAC. Once set, you can navigate to the DRAC via web browser and use the VIrtual Media.

Todd