I was just reading up on linux and found an interesting article:
"Why does the installation program keep asking for the cdrom when it's already in the drive, or states it can't find a file?
If your system uses a SCSI cdrom drive, or an older IDE cdrom drive, it's possible that the correct module was not loaded during hardware setup and your cd drive is not enabled. You may be able to determine this by viewing the boot messages in one of the virtual terminals. This is done by holding down the Alt and Control keys while pressing, one at a time, the F1 through F10 keys. You should see different text messages on each virtual terminal. Look for indications that your cdrom drive was detected and a module loaded, or an error message indicating failure. If this occurs you will need to either find the correct module for the drive, upgrade to a newer unit, or use a different installation source.
Not being able to find a particular file is usually an indication that the cd is corrupt. You should have checked the MD5 sums before burning. If the MD5 sums are correct, then there could have been a problem during burning. View the cdrom in whatever OS you are running. If you see one large .iso file, you've copied instead of burned the disk image. Even if you see files and directories and the MD5 sums checked, a file or directory may have not burned correctly. I do not know of an easy way to 100% verify each file and directory was burned correctly.
There could be a problem with the cd media itself. Don't burn at a speed that is faster than the rated speed for the media you're using. If you use a cdr-w, make sure there are no smudges on the burning surface _before_ you start the burn, and, just to be sure, blank the disk before burning your iso file.
Another possibility is that your cdrom has problems reading from the media you're using. Try using the cd in another cd reader, or another system to see if this is the case."