I can't find any traces of the application and its official website is unreachable, which generally means that the product is no longer available. So, if you had the installer stored on your computer, you should hold on to it. In case you don't and you're looking for an alternative, I noticed that many people have chosen to use LogBook Pro Desktop instead.
As far as getting your files back goes, I recommend connecting your old hard disk to a different computer and try retrieving your data using a file recovery tool like Disk Drill. In case you don't have the installer, you could try retrieving the installed version of FlightLevel 2000 and maybe you can get it to run on a different computer. The chances that it will work are very slim, but it's still worth a shot.
