By going back in time and backing up your originals! Seriously do it!
But yes, redistributing original files is against the rules here at the NLSC viewtopic.php?f=22&t=2 but it is possible to regain original files without asking here.
Here is a video tutorial on how to get original files from your Disc, and Steam, without having to reinstall and deal with 2K Support of the reinstalling needing a new CD Key issue.
http://www.youtube.com/watch?v=XI7Rvl-saOI