Sorry, but you need the 2nd disc. I don't think there is any way around it because when it wants to load your progress it needs the 2nd disc, the person that put the game on 2 discs really messed it up with that game.
I even have a glitch of my own. When I go to play the game, I put the 1st CD in, load my game, then it says to insert the 2nd CD. Once I do that I get an error saying that there is no disc inserted. But that's okay because I'd be playing it on PS3 not PS or PS2, and when you play D2 on PS3 the glitches are terrible, so I stopped with D2.