Re: Gateway processor upgrade suggestions
It would still be more cost effective and the gains in performance would be far better if you just bought an inexpensive AM2+ or AM3 motherboard and an Athlon II X2 or X4 (or Phenom II X2 or X4 depending on budget) compared to what you'll pay and get with a Pentium D, which isn't even guaranteed. The P4 architecture, even in dual core trim, can't hold a candle to what the Athlon II can do, and in some cases can even be cheaper if you get a good bundle deal. I built an Athlon II X2 at work a couple of weeks ago and it absolutely shatters the performance of the P4 3.2 GHz it was replacing, and completely lays waste to some of the Core 2 Duos we have in house as well.
WoW is processor and RAM dependent for sure, and a good GPU will help in the long run as well. I have a Phenom II X4 940BE and a Radeon HD 5870 and it still has issues with some areas of WoW (but I have a 27" primary monitor) but a P4 just can't cope with the demands.
Your motherboard will not support a quad core. You could try, but I doubt the results will be favorable. I used to work for Gateway.