This is very strange, let me write down all the details as much as I can.
A friend told me that his computer can not access some websites, like Yahoo, Google, IBM etc, but he can access other websites like Shaw.ca, cibc.com etc.
He use Shaw Internet without router, the IP address is obviously public. The OS is Windows XP professional SP2 Traditional Chinese Edition. The IE version is 6.0.2900.2180, 128bit.
Without doing any configuration for this computer, we moved it to my network environment: Telus Internet plus a router, so it gets private IP address, like 192.168.1.x, but now every websites can be accessed.
[Not finish yet]