[LinuxVadaPav] Why CD dose not boot when it copy CD on Hard disk and then write?

[sachinkhot]

I copy all files and folder of 'Redhat Linux 9' 1st cd on Hard disk. 
Then it write on CD with Nero.
When I try to boot that cd (which I write), it dose is not boot.

(When I copy cd and then write, it works)

Why it dose not boot when I copy contents of CD on Hard disk and then 
write?

Please help.

Thanks in advance
Sachin