APRSISCE/32 triggers Windows sounds (MessageBeep - http://tinyurl.com/dx7sjrh) on various events. Eventually I hope to support custom sounds, but for now you live with what you have configured in Windows:
GPS Locked - MB_OK
GPS Lost - MB_ICONWARNING
APRS-IS Lost - MB_ICONWARNING
APRS-IS OK - MB_OK
Inbound Message Received (for ME) - MB_ICONINFORMATION
Outbound Message Ack Received - MB_ICONINFORMATION
New Bulletin Received (if Enabled) - MB_ICONINFORMATION
From MessageBeep's page:
MB_OK - The sound specified as the Windows Default Beep sound.
MB_ICONINFORMATION - The sound specified as the Windows Asterisk sound.
MB_ICONWARNING - The sound specified as the Windows Exclamation sound.