A piece of advice, though not necessarily related to reinstalling Oblivion. Before you go too far, set up a separate partition where you can install your OS, something like 50-60 gig, and use the rest of your hard drive for your programs etc. That way if anything ever happens to your system the only thing you lose out on is the contents of that one small partition, all the rest of your data will remain intact. Your data partition will remain unaffected by viruses since those usually target only your C:/ drive, which is the one that will have your OS, and ignore your other partition. Then, in the event of something like this, all you would to do is reinstall the game to the same location so the registry knows where to find it, and everything would already be in place.