Not sure whether it has anything to do with vista or not, but I just tried Eps 3 and 4 on my new laptop, and neither seems to run very well. The audio tends to break up very easily, and if I try increasing the resolution past 1024x768, the game slows to a crawl. I could understand on an older machine, but this is a Core2Duo 2.16 laptop with 2 GB of RAM, NVIDIA Quadro NVS 120M (driver version 126.96.36.19946). Audio is through the onboard Dell card. I'm not seeing the CPU spike when I get either the video slowdown or the audio problems.
Any idea what's going on here? Anyone else run into similar problems?