virtualbox.org

I installed VirtualBox by means of synaptic, which placed a launcher in the Accessories menu. I click on the icon, and there appears a window with VirtualBox OSE written on top. I click on File -> Virtual Disk Manager => CD/DVD image and add an .iso filename.
I click on the "New" button and a window with "Create New Virtual Machine" pops up. I specify name, operating system and version (for example, Zenwalk, Linux, Linux 2.6). I specify memory size (256 MB). Then boot hard disk, use existing hd. Now it summarizes the specifications so far. I click on "finish". The pop up window disappears. Now I see "zenwalk disconnected" on my left, with Details on the right. The boot order is: floppy, CD/DVD-ROM, hard drive (funny). Now I click on Start. A window with "zenwalk (Disconnected)" pops up. An information window pops up explaining about the host key. I click on "OK". zenwalk tries to execute and stops with the message "FATAL: no bootable medium found; system halted."
I had a bootable CD on the CD reader, and an .iso file chosen, and yet, it says there is no bootable medium.
I have tried this many times, always with the same result.

What am I doing wrong?
I have previous successful experience with VMware, so this is not making sense.

The Virtual Disc Manager only makes an ISO file known to VirtualBox, but doesn't associate it with any VM (plus adding CDs this way is more or less gone in VirtualBox 4.x).

What you need to do is choose your VM, open it's settings, go to the "Storage" page, select the CD device that should have been added automatically and choose your ISO file on the right hand side - that'll "insert" the CD into your VM's disc drive.

Of course, reading the fine manual that should have been installed by your package manager would probably have helped you sooner than starting three threads about the same problem, expecting people to react in a matter of mere minutes...