I lost my Oblivion installation CD, Am I screwed?

[BillNye]

Last summer I played quite a bit of Oblivion (PC). I lost the Installation CD and thought nothing of it. Later somehow my file was deleted, Can't remember how, but I quit playing anyways, now I'm craving this game, is there anything I can do or would I have to rebuy the game. Also does the game require the regular CD to play? I forget.