I remember back in the days when I had free time, I decided to shop around for an RPG. It was a toss between Baldur's Gate and Morrowind. I heard about the open-endedness (is that even a freakin' word?) of Morrowind, so it one the day. I remember when I first popped it in and my GeForce3 starting spewing out frames.
I think for the first week solid all I did was take screenshots. I wasn't so much a player character as I was a tourist.
Now, believe it or not, I'm sitting here doing production code moves and listening to the Morrowind soundtrack in VLC Player. Even if I can't play I'm still hideously hooked. That's how freaking engrossing Bethesda makes things... they put your cortex right in the world they created and never let it go.
That's why I fear Oblivion. I may lock myself into the den and never reappear.