virtualbox.org

I have windows 8 and I tried installing the virtual box with Linux-Ubuntu.
I gave it 1024 MB of RAM and 40 GB of hard drive.
As I start the virtual machine it gives me that message: "Fatal: no bootable medium found! System halted."
It appears on the black screen and does not carry on.
Can someone tell me what should i do?

The message means what it says - there is no bootable disk (or other medium) attached to the VM. If you are installing Linux then you typically need to download a Linux ISO and mount it in the VM as a virtual CD (using the Storage settings), then start the VM.