Windows 2000 terminal server

When I run tscc.msc on our Windows 2000 terminal server, and go under the
Connection tab, and right-click on RDP-Tcp and select Properties, and then
select the Client Settings Tab, there's a section called "Disable the
following" and "Audio Mapping" is check-marked to be disabled.

However, it's grayed out so I'm unable to REMOVE this check-mark to enable
audio mapping. I'm logged on as
administrator so I don't understand why it's grayed out.
Is there a way to get and change this setting?

Thank you

Excerpt ftom RDP-tcp (TS Connections) Help:
This option is supported only for Citrix ICA-based clients. Specifies
whether to disable client audio mapping. By default, this feature is
selected.

Excerpt ftom new RDP client Help:
Depending on the policies of your network, audio redirection might be
disabled for some or all remote connections. Additionally, audio redirection
does not work when you connect to a server running Windows 2000 or earlier.