Q: My Windows 7 PC suffered a failure of the main circuit board and some damage to the hard drive. I lost a lot of data (photos and genealogy files) because a computer technician was unable to recover them from the hard drive. I wondered why the technician was able to recover so little data. Why could he find some pictures, but not all of them? I also was surprised that during the recovery process, many notices said that we did not have the permission to see the files stored on disk drive. Why not?

If I had made a back-up of the data, could more data have been recovered from the hard drive?

MARGIE BRATLAND, Chanhassen

A: A recent back-up of your PC's data (to an external hard drive or a USB flash drive) would have made it unnecessary to recover the data from the PC's damaged hard drive. In addition, the back-up process might have given you an early warning of the PC's problems by notifying you that some files on its hard drive couldn't be copied (signifying that they might be damaged.)

But without knowing more about what happened to your hard drive, I can't say exactly why you couldn't recover more data. For example, was the disk damaged by an electrical short circuit between the main circuit board and the drive? Or did the hard drive suffer a "head crash" in which the disk's read-write head stops floating above the disk and strikes the disk's surface?

But any damage could have hindered recovering the data stored on the disk. Here's how:

Normally Windows creates a directory for a hard disk that lists where each file is stored. As the hard disk fills up, newly stored files must be broken into pieces that can fit into available disk space. But even then, the directory can locate where all the pieces are.

The success of recovering files from a damaged hard drive hinges on whether both the directory and the stored data are intact. If the directory has been destroyed, the disk recovery software faces a harder task: It must search the hard disk looking for the different pieces a file, then try to reassemble the file as if it were putting together a jigsaw puzzle. If even one piece of a file can't be found, the entire file is probably unrecoverable.

That would explain your data loss. But why didn't you have "permission" to view some your own files? In Windows, individual files are stored in file folders. Each of these folders has a security component that determines which users of your PC have access to a particular folder. If damage to the disk obliterated a folder's security information, your "permission" to access the folder might no longer exist.

Q: I paid to be a premium user of the Microsoft Mahjong puzzle game on my Windows 10 laptop (premium eliminates advertising and gives other perks.) But after some Windows updates, the game's premium option quit working. Microsoft has been of little help. What can I do?

SHARON FERGUSON, Woodland Park, Colo.

A: Open Settings, choose "Apps" and click "Apps & Features." From the list, choose Microsoft Mahjong, click "advanced options" then choose either "repair" or "reset." Restart your PC.

If that doesn't work, go to the same location in Settings and uninstall Microsoft Mahjong. Restart the PC. Reinstall the game from the Microsoft Store (tinyurl.com/yeyuh8f4). Restart the PC.If that doesn't work, you can troubleshoot the premium Mahjong app by following the instructions at Microsoft Casual Games (see tinyurl.com/2p8zy2js).

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