HpbImgPreload('HPB_ROLLOVER1', 'img/voice_button1.gif', 'img/voice_button2.gif');
HpbImgPreload('HPB_ROLLOVER2', 'img/clear_button1.gif', 'img/clear_button2.gif');
HpbImgPreload('HPB_ROLLOVER3', 'img/free_button1.gif', 'img/free_button2.gif');