I am running Bobcad with Vista 64 bit and when I go to 3d it does slow down a lot. I run my power plan on high performance which helps some and when you start a new drawing use the save as and save it with a name and every now and then just cick the save icon and you will not loose much when it does that. There are some things you can do in Vista to help its overall performance. I did a search on the internet for speeding up Vista and found some good stuff.
I have been told that laptops suffer when it comes to any type of demanding software, and that it would run much better on a full tower system.