According to the manual (pg. 5), there are four small icons/keys to the left of the right speaker, just above the function keys. Use the small communications key (left most icon, just between the F10 and F11 keys) to toggle wireless on/off.
http://support.acer.com/acerpanam/Manuals/acer/2009/UserGuides/AS_3810T_3810TZ_3410T_QG_Eng_0402.pdf