A ? means the EFI can't find a disk with the OS on it to boot from. Boot from the original CD and run disk utility, repair the disk & permissions, and see what's up. You may need a more powerful disk repair utility like Tech Tool Pro to actually fix whatever corrupted it.
Or worse, the drive could have failed. If you have an external HD USB or FW, boot to that and then clone the whole disk to it for a backup. She may have lost everything.