Considering the 8600 GT scored a 257 on a G3D Mark test, that should justify in itself where the problem lies, but just in case OP isn't on the ball with how out of date that GPU is.
According to wikipedia, the GeForce 8 series was released in November of 2006. As for the 8500 and 8600 those didn't debut until April of 2007. And for any benchmark on recent games, any articles pertaining to the card and benchmarks were written between the times of 2007 to early 2009.
The game is either crashing due to low end hardware, or uplay is a naturally known piece of stuff to begin with. A fix I found via steams community forum using basic google searching because OP obviously lacks in that easily applied skill, is that check and make sure your monitor resolution is 16:9 and not 4:3. Otherwise, check drivers and make sure all is up to date running fine.
