.Ubuntu restored my hard disk solved no hard disk error

this is not actually a problem but a question on a solution I have found that. I just want to understand what is happening in the back ground. Problem is that my computer didn’t boot. Service person told to come after a day. But he later said that his hard disk is gone. Since I didn’t had money for new in right that place, came back home. Just tried once installing Ubuntu. Set some extension as file system. I think ext3. And then inserted windows OS CD. The hard disk got detected, got formatted and now windows is running perfectly. Not found issue till now. My question: What has happened to my hard disk? How did it start working? Any thoughts?
