ok.. Mutitasking is near Impossible with games when they are set to run fullwindow.. mostly always.. YOu can try to run WOW in windowed mode if you have that option should take up less resources but..
This is Not a hardware issue.. It is due to the fact most MMORPGS use pretty much ALL cpu resources they can get and a huge amount of VRAM/memory buffer..
the only way you can multitask without extreme lag is to get another PC. Or try mimizing the strain WOW puts on a PC. Minimal Settings etc
Since you have to keep in mind It's still writing to memory and using CPU recources and Very heavy draw from the system..
Things that can be multitasked are stuff that use 10-40% of cpu resources..
Non fullscreen games or fullscreen games that aren't 3d
Videos, MP3 , internet. etc...
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