Random Crashes, No Mods Intalled

So I've just started trying to get into playing Planescape, but the game keeps crashing for no clearly discernible reason. It crashed twice when I tried to overwrite an older save file (but worked fine when made a new save and overwrote that), and it also crashed several times when I attempted to enter a building. I have no mods installed whatsoever, and I'm playing the DVD version on my Windows 7 desktop. If further details are needed for you to help me solve the problem, I'd be happy to supply them, but I have no clue what the issue might be. If you can help, that'd be great, and it'd also be cool if you could explain exactly what the problem is if you have a solution, because I'm interested in software design and I'd like to learn what I can from the solving of this issue. Either way, thanks in advance if you can help.