I installed MySQL 5.0 on second hard disk long time ago, and three days ago the OS had to be re-installed because it got trashed. I don't want to loose all the data I have in the earlier installation. How should I proceed?
Not sure I follow what you are saying here? When you reinstalled did you still have a copy of all of your data files or did these get trashed too? If you still have the data files then you need to copy these across to the root of your mysql data files folder and then attempt an upgrade of these data files.