win2000 not booting from disk

Hi,

I am trying to boot my win2000 prof pc from boot disk and it will not work. I get this message, Disk I/O Error and that’s it! once I unplugged the cdrom drive and it came up but then I got a different error message(didn’t write it down) and then it never came up again. Any ideas? also it will not boot from the cdrom either!