Win2K terribly slow logons

I’m expiriencing long logons in to our domain, about 15-20 minutes so everyone is then logging into thier own computer locally. The situation is that we recently set up Active Directory on our server. We are on a DSL line and the DNS servers we use are located at our ISP. Microsoft’s site said that the problem was DNS related. But I’m not sure how. There is traffic going throught the server, but after the fifeteen minutes the computer times out and logs in locally. Does anyone have any suggestions? Please help I’m new and really frusterated.