You can set it manually too: ctrl + alt + del > Click Wow.exe > Rightclick > Set Affinity... > Check desired Cores. I personally use Core 0+1 for main + secondary alt, and cores 2+3 for the last 3 alts; no noticeable difference and no hiccups.

8500gt 1gb ddr2 ram < 8800gt 512mb DDR3 ram. XFX slightly-overclocked 8800GT 512mb DDR3 on Newegg = $180ish(with optional rebate after the $180 I think); same one I bought and despite it being HUEG LIEK XBOX LOLZ(it's as long as my whole freakin mobo and as stall as the case is wide almost...I had to do some mighty careful SATA-cord maneuvering around it when I installed it) but it's worth it; again haven't had any hiccups. Definently upgrade the vidcard if nothing else, and I, personally, recommend going with 8800 vs any 9x00 series; based purely on what I've read, they don't run much better than 8800s, and an 8800 is overkill for WoW as it is anyways...no need to pay more for what you don't need

2gb ram is also bad for more than 3; newegg has G-Skill 4gb dual-channel ddr2 800mhz on sale for a measly $80, grab it while you can I paid $100 for 2gb last year so 80 for 4gb is a great deal, ram's cheap right now lol

I also recommend using maxfpsbk 20 on all windows, including your Main, since it's only the fps while the window is not up front.