how to reinstall - original DVD's no longer work

[Farkenal]

Hi all, I purchased the game years ago, though now I have a brand new PC and when I went to install the game with the disks, I got an error message on one of the files, something like dat4

 

So given that my disks no longer work, I was wondering if there was a way I can activate the game via Steam with my cd-key or something like that

 

Any help would be greatly appreciated