Man, I'm looking at that and don't see anything that would be obviously sucking for one copy of WoW. The integrated graphics is the latest gen from Intel. You have low RAM but not so little that it would do what you're talking about that I can tell. The CPU might be the problem but it shows as being faster than an Athlon X2 4000+ so I'm thinking that's probably not the bottleneck either.

Have you tried tweaking down the graphics options in WoW on that machine? Also might try running it at 1024x768 instead of 1280x1024 if that's what you're currently running. Also, how much memory are your addons taking up?