if your ISP have problem with DNS, you can use public dns for name resolution.

Google Public DNS (Recommended)

8.8.8.8
8.8.4.4

http://code.google.com/speed/public-dns/

Level 3 Communications

4.2.2.2
4.2.2.4
4.2.2.6

OpenDNS.com

208.67.222.222
208.67.220.220

To add DNS server, take property of your LAN Card, Click “Internet Protocol (TCP/IP)” click the button property. On next page, you have option to specify your own dns server.