Battlefield 2142 Redemption

(I know I selected Battlefield 1942 as the product, but Battlefield 2142 isn't listed and it wouldn't let me subit my query otherwise. This question refers to Battlefield 2142.)

A little over a year ago I was having trouble getting my Battlefield 2142 game to work on my PC. Since then I have gotten a new PC and I wish to install Battlefield 2142 on it, but Origin does not allow me to redeem the serial code given to me back when it was still EA Download Manager. As you can imagine this frustrates me, and I would like to know how I can install the digital copy onto my current PC.

Thank you.