Why on earth would you towerize a 2000?
It's original Desktop case has ample room for any upgrades you may want and is so strong you could use it to prop up your car while you changed a wheel.
If you're desperate for space, just tip it on it's side. :-)
I can't believe it would be for aesthetic reasons, the case would have to be huge, and probably beige.
Still, if you do decide to go ahead, please post plenty of pics, it's always entertaining to watch.
