What kinda lag is it? Just fps drops or game freezing badly like it's loading too much?

I only had problem with the last part, FPS drops never been a problem. My specs are:
(CPU) 4-Intel® Core™2 Quad CPU Q6600 @ 2.40GHz, 2399MHz, 0KB (0% Load) .:. (RAM) usage: 1077/2048MB (52.59%) .:. (GFX) NVIDIA GeForce 8800 GT, (Display) 1152x864/32bit/75Hz (I'm only running 2 WoW clients)

My settings in fraps:
Full Size, 60 fps, No cursor + No sync both checked, and record sound unchecked (but I don't think that matters)

Now I tried arranging fraps and WoW to different CPU cores, nothing really helped but the problem was simply where I set my uncompressed files to be saved in.

At first, I had major lag while frapsing when the frapsed materials were saved in C:/ so I changed it to D:/ instead and it worked fine. Then for some reason after upgrading GFX drivers it started to lag again and I was trying to figure out the problem for hours, but then it was simply change it back to C:/. Even though it should be best that frapsed material are saved in another disk while frapsing.

Misc info, when I start my WoW clients, I set WoW1 to CPU 0 + 1 and WoW2 to CPU 2 + 3 and fraps is using CPU 3, sometimes I set it to use all CPU's but haven't noticed any difference.

If that doesn't work out for you, I simply don't know sorry.