I try to re-install but it wont detect my CD rom.
You said the above in your first post, but now you say that your CD drive is functioning. Either your install DVD is the problem or it's the drive. You need to use your install DVD to boot the machine so as to run Disk Utility and check the hard drive.
I think because of the broken english the OP means (or more so what i took from it) is there drive works but won't recognise there Install DVD ?? Maybe I'm wrong.
@OP as chscag mentioned look for scratches and damage to your Install media.