I´ve got a PC an installed a Hackintosh. (don´t worry i´ve a Macintosh too. hackintosh is only project caused by boredom).
the interesting thing is that guildwars runs in 6.1 on my hackintosh with all sounds. and once or twice in fullscreen too. (that was after playing fullscreen in windows, rebooting and playing without -windowed).
the soundcard i used is a onboard realtek hda from the Asus P5W DH Deluxe board.