Cannot access Internet in a LAN, while others can

When I set up computers for my house mate today, a very strange problem occurred. Three computers were connected to a local network, all can open the modem admin page. However, only two of them can access the Internet, the third one cannot. Also the third one cannot join Windows 7 HomeGroup. It will tell you the password is incorrect, but you are 10000% sure you typed in the correct password. Furthermore, there is a second network named "Unidentified Network" showed up besides the original one, though you only have one adapter.

Probably 99 in 100 people will blame Microsoft, and claim HomeGroup is buggy, don't use it. The problem is that, we need to 'thank to' Apple on this issue. Surprising, isn't it? This issue is caused by Bonjour, an apple from Apple. Follow the post at http://nw360.blogspot.com.au/search/label/bonjour to remove the unwelcome software.