No, there's only an X-Box 360 version.
As for computer games, you don't have to upgrade every 2 years, that's only if you want to play the latest games at full detail, which is usually just the first-person type games as those are the most demanding. You can usually play other style games fine, it's just that first-person games are so popular and are becoming integrated into more style games these days, such as this, Oblivion, being an RPG.
You would have been fine with a 2 year old machine, it's just that your integrated video card is what's killing ya. An ATI 9800 series card is 2 years old and they're able to still run Oblivion, just not at the best detail, so if you would have had one of them 2 years ago, you'd be able to run it, but you're lacking an independant video card.
So either $150ish for an ATI 800GTO or $400 for an X-Box 360 (or however much they are these days). I wouldn't recommend anything less than the 800GTO for this game.
- N