Spark SIP-Plugin: Headset and Ringing Device

Are there hidden Configuration Files for setting up a Headset and Ringing. Ihave Spark and the SIP-Plugin installed on our Client PC´s. Spark is connected to the Openfire/Asterisk Server. While using free SIP-Client Zoiper everything is fine. I can select the USB Headset for Audio and the prime Soundcard for Ringing.

Experimenting with different settings in Windows XP SP2 (Audiosettings) and several restarts of Spark it is NOT possible to set this up.

Please HELP