Change default sound card on all windows user accounts

Hello

I am trying to find a reliable method to change the default windows
sound card for all users who log onto windows that dont have
administrator rights.

I have added an additional sound card to a computer (a voip phone) and
windows switches all playback to the new sound card by default. I want
to make the original onboard sound card the default again. This is
simple on an adminstrator account - I go to 'control panel' then
'sound and audio device' then choose the correct sound card as the
default.

This works on the administrator account, but if anyone elso logs in,
the default sound card is the newly added sound card ie the change on
the admin account is not propagated to all the other user accounts.

The computer has a lot of user accounts, and the only solution I can
think of is to grant every user admin rights, log on to each user
account, then change the default sound card, and finally remove admin
rights.

Anyone got any ideas as to how I can change every user account in one
go?

Thanks

Paul