Vista - VoIP sound problem

Hi,

I have just installed a Butler 4012 VoIP telephone to run with SKYPE but am
unable to receive any sound through it. The phone seems to be connected to
the SKYPE program properly as I can dial out with it, I just can't hear
anything with it. I did play about with the sound devices and got to the
stage where I could fully use the phone, but I then couldn't hear any of
the usual sounds the computer makes e.g receiving new email or playing
iTunes. My OS is Vista Home Premium SP1. My speakers are separate from the
monitor.

Thanks for all help given.

David