Setting affinity on a quad core can help but I dont know how affective it would be on a dual core, I would just leave it alone and let windows decide for you.

If you open up keyclone and go into setup then command editor you'll see 2 fields called maxfpsbk (how much fps your slaves can go up to) and maxfps (how much fps your main can go up to). Setting maxfps on all wow regions to 30-40 and slaves at 10-15 should help you a TON.