BitTorrent Forums: older torrents won't seed - BitTorrent Forums

I used BitTorrent a couple of years ago. I stopped downloading for awhile and I think I uninstalled BT. Anyway I decided to get back into the game and had to install BT again. I added all the old downloaded files so that I could seed them, but they won't go. Newly downloaded files seed just fine. The older files show up in BT with a dark red line as opposed to the green line with the newer files which are seeding. How do I get these old downloads to seed again? Is it even possible?