Default domain for user accounts

Hi,

I am trying to set the default domain for user accounts so users don't neet
to prefix their username with domain\ or suffix them with @domain.com. I
have gone to the Authentication Methods tab and enabled both clear text and
digest authenticaion and set the default domians to the DNS name and have
also tried the netbios domain name (domain\). Neither work. Instead,
usernames are being prefixed with the fqdn of the site, i.e.
srvr.domain.com\username.

What do I have to do to enable this?

TIA,

Jarryd