Incorrect. It's not the company's PC, it's yours. You get to do as you will with your own PC (legally speaking).
Now, it's probbaly illegal to hack into WoW's PC's to stop the communication with the software that they installed on your PC...but stopping something on your own PC is a different thing altogether.
True,
"You get to do as you will with your own PC (legally speaking)"
except when you sign away those rights in exchange for services, as a condition of those services....although some of those EULAs surely are illegal and unenforceable...
...until we have the ICANN/UN/Clinton e-KELO electronic eminent domain ruling...God forbid!