I'm a big fan of the original theme, the slower, more emotional theme from the first few episodes of the series.

The second theme was standard 90's fare.

Hmm... I hadn't really noticed the change in theme songs but now that you mention it, I vaguely recall that the music was different. I'm anxious to get the DVD's so I can watch them again. Right now I'm just going through the tons of eps I have on my DVR.