I occasionally run KR on a 3 1/2 year old Gateway M460 laptop. It has 1 GB of RAM, upgradeable to two but I haven't gotten around to doing that yet. The operating system is Windows XP Professional. If you want to know more about the machine I'm using, just PM me and I'll try to figure it out for you. Not too much of a techie when it comes to figuring out where to find and interpret a lot of the system specs.
The only times I crash with KR running are when there's way too much going on in the way of sounds and particle effects, e.g., in Destard with about 8 snarling, snapping, spell casting things piled on top of the tamer and pet. Haven't tried using KR in a really big group setting like an event. Probably won't try it either unless I upgrade the memory.
Be sure to read the thread in the KR forum about optimizing your setup. Good info in there and it helped me quite a bit. (
http://vboards.stratics.com/showthread.php?t=122985)