This is an easy way:
Open Internet Explorer, in the menu click on Tools choose Internet Options, click on the Connections tab, in the Internet Options Window click select the dialup settings (in my case there is only one but who knows you might have more
) now choose Settings.
In the next window you'll be able to see proxy server settings. In order to see the DNS settings you need to go one step further. In the same window look for Dialup Settings (right under the proxy server settings) Next to the username click on properties. That will take you to your modem settings, from there under the general tab check if the Use Area Code and Dialing Properties is checked or not and modify the Dreamcast internet settings accordingly... Now click on the Server Types tab and at the bottom click on TCP/IP Settings- that's where your DNS setttings are.
That's about it, also note that there are different ways to do this like through control panel... use whichever you find easier.
I'm not sure about blind dial, but i reckon you should leave it as it is coz i clearly rememeber that I didn't mess around with it.
I hope this makes sense