How can I fix a damaged hard disk so it will work again?

 This question is becoming more and more popular with people upgrading computers and moving drives/information from one computer to another. This can be an expensive repair if you end up using a company to recover the data. But a good way to prevent this issue from arising is to perform regular maintenance on your hard drive(s). Also creating a regular backup of your data allows you to retain your data even when the hard drive fails.