Windows 7 Internet Connect Issue

I have got a Dell desktop computer for 2 years and worked fine before.

Recently, the hard disk was broken down and Dell replaced a new hard disk for me. As the hard disk was replaced, the Windows 7 (64-bit professional) was needed to re-install. Afterward, there is an issue for the internet connection.

When I connect the computer to the internet via the router or directly at the port, it works okay for the first 10 to 15 minutes. Then it stops. If I click refresh at the browser, I need to wait for a few minutes until the connectivity active again, but it lasts for 1 to 2 minutes only, and stops again.And I need to wait for a few minutes...and so on.

 

If I connect the internet via the router, when this problem occurs, it will effect the other computers (Windows XP and Vista), no matter via LAN or wireless. None of the computer can connect to the internet. And when the Dell computer is able to connect to the internet at that "1 to 2 minutes", the other computers can connect as well, also for that "1 to 2 minutes"

 

If I turn off the Dell computer or unplug the cable from the Dell computer,, other computers work perfect.

 

I thought it might be the network card problem, So, I tried the USB Ethernet Adapter instead. However, the same problem still occurs. Hence, I guess it may be caused by Windows 7.

I am sure it is not my ISP's problem, not the router, not the cable, and should not be the network card (unless the connection via USB Ethernet Adapter still need to go through the network card)...

Is there anyone knows how to fix it? Please teach me in details, thank you.