I played through probably 85% of the game a couple years ago, but during a move one of my cds broke and now I can't finish the game. I kept my save files and recently got a new copy of the game but am having trouble importing my saves.

I put them in the saves folder and you can see them in the load games window but every time I try to run them the display goes crazy and the game crashes with no error message. I never have ran any mods or anything so I can't see why this would happen, is there something else I need to modify to run old saves?

Well, if you never had any mods and right now, the new copy, is also free of mods, maybe it's a game version difference? If i recall correctly, there was an official patch for PST 1.01 or something like that.
Maybe you don't have it now, or you were playing on v1.0 in the past.

Also, some people say, that the 4CD and 2CD version are not exactly the same. Problem may be hiding here also.