that that is a removeable storage medium
the same CD isn't permanatly mounted in that drive
a hard drive is considered a non-removeable disk, as it doesn't have exchangeable media (you can't pop it open and change the platters to change your data) while CD, DVD, Floppy, Zip, Jaz, Tape and a few others are removeable
their storage media can be changed out
I installed a DVD recorder as master and made my CD-ROM the slave. Both work fine, have burned a test with the DVD and viewed a couple CDs.
However in Explorer the CD-ROM is now named Removable Disc. Why is that?
Tks.

Chowhound
Comic Vine
GameFAQs
GameSpot
Giant Bomb
TechRepublic