After getting grey screen with flashing ? inside file folder, I inserted my Operating Disk in CD drive, was able to get to the purple screen and choose Utilities. I ran Verify Disk and rec'd this msg: "Invalid B-tree Node Size. The volume could not be verified completely. Error: the disk needs to be repaired." Upon running Disk Utility after a few minutes, I rec'd a popup box saying, "Disk Utility stopped repairing disk0s2. Disk Utility can't repair this disk. Back up as many of your files as possible, reformat the disk, and restore your backed-up files." My question is: How do I Backup Files if the HDD isn't working? Advice would be greatly appreciated.