I think you're confusing the actual clock speed of the RAM with the Data Rate.The data rate of the RAM, which is used when they say the RAM is DDR2-800 or something is actually TWICE the actual clock speed of the RAM (and 4 times if you go to say... GDDR5 on a graphics card). So a DDR2-667 module runs at 333 MHz, a DDR2-800 module runs at 400 MHz and so on. I don't believe actual 800MHz or 667 MHz DDR2 RAM exists for laptops since I know my desktop won't post if I try to clock my DDR2 higher than 450MHz!
Double data rate - Wikipedia, the free encyclopedia
You said your RAM runs at 333MHz, so it is DDR2-667 already. Going to DDR2-800 won't help things at all, given that DDR2-667 vs DDR2-800 barely does anything for low-end quad cores, let a lone dual core laptop CPUs. This difference has been benchmarked, but I don't know any links off the top of my head.
Your bottleneck with WOW is more likely GPU than anything, unless you're running with something like 512MB of RAM - then you'll want MORE RAM and not faster RAM.
Also, I wouldn't trust the Windows Experience Index at all - when it says my SSD is slower than my old Samsung F1 1TB hard disk, something is wrong!