Kernel panic error

when I insert CD and boot the machine, I am getting the following error.

Kernel panic - not Syncing:VFS:Unable to mount root fs on unknown-block(1,3)

Can I know why this?

-shivu

Sorry, This error was because of CD burning was not happenned properly.
While copying CD, it throws error, But I neglect that. Finally I got because of that error The behavior was like this.
So, once again I burn the CD and now I am able to boot successfully.

thanks
-shivu