[Windows Vista] How to diagnose Network problems?

Network and Internet connection problems can be solved in Network and Sharing Center of Control Panel. Network and Internet connection conditions can be checked and Network status can also be displayed on the screen.
Please see this FAQ for more details - [Windows Vista]How to ensure that Network and Internet connection conditions.
1. Click the Start button and click Control Panel.

2. When Control Panel appears, click Network and Internet.

3. Click Network and Sharing Center.

4. The Network and Sharing Center screen will appear.

When the Network cannot connect normally, a red “X” will be displayed. Click the part marked by the red “X”.

5. When the Windows Network Diagnostics screen appears, it will start to scan problems on the Network.

6. When the scan is complete, the results will be displayed. According to different usage conditions, the displayed message will be different.
7a. When problems are detected.
 The detected problem will be displayed and methods to avoid this symptom will be provided.
b. When no problems are found.
The following will be displayed.