Can't change graphics settings

[Rapid17]

So the game crashed on me a little while ago, which happens quite often so I thought nothing of it. However when I re-entered the game the grahics were very muddy, so when I checked my graphics settings it was all set to low, rather than high. When I tried to change it, it stated that I can't change the graphics on a 32-bit operationg system, but I'm running windows 7 64-bit. I tried restarted the game as well as my computer but it still won't let me change it. =\ Anyone have a solution?