I know the game recommendations are listed differently than the requirements.  I just want to point out that while 1 gig of ram might be the minimum requirement in vista, if the 1 gig is shared with a video card on a laptop, it is not sufficient.   As soon as a game on a large small map or a small medium map hits midpoint, the memory requirements are too much and the system will begin paging heavily resulting in severe lag.

2 gig kit is on the way, will report how well this remedies the issue.