Can't de-authorise Digital Editions on PC that crashed and now it doesn't work on new computer.

I installed Digital Editions and then my PC crashed. I downloaded it onto my new computer but when I try to open the e-book I get a message saying E LIC ALREADY FULFILLED BY ANOTHER USER. I was told to de-authorise DE on the old computer but I can't because it's totally kaput. How do I get DE to work on my new computer then?