Won't fit slot ?? Sounds like a type that you insert the CD part way and it draws it in the rest of the way.
Open Windows Explorer, right-click on the CD-ROM drive, click on "eject" as there won't be room for 2 disk in the drive.
You don't really have a CD-ROM drive, just an older Zip drive or a tape backup.
To open Windows Explorer, Right-Click the start button, click on "Explore" (right below "Open")