Manual method to Reset TCP/IP for Windows XP/Vista/7

 Manual method to Reset TCP/IP for Windows XP

Note:This section is intended for advanced computer users.

Open command prompt, click Start and then click Run. Copy and paste (or type) the following
command in the Open box and then press ENTER:
  cmd

At the command prompt, copy and paste (or type) the following command and then press ENTER:
  netsh int ip reset c:\resetlog.txt  

Note: If you do not want to specify a directory path for the log file, use the following command:
    netsh int ip reset resetlog.txt
Reboot the computer.

Manual method to reset TCP/IP for Windows Vista and Windows 7

Follow these steps to use the reset command to reset TCP/IP manually:

Open a command prompt, click Start and then type cmd in the Search programs and files.
 Right-click CMD.exe icon in Programs and choose Run as administrator. 

When the User Account Control box pop up, click Yes.

At the command prompt, copy and paste (or type) the following command and then press ENTER:
    netsh int ip reset c:\resetlog.txt

Reboot the computer.

When you run the reset command, it rewrites two registry keys that are used by TCP/IP.
This has the same result as removing and reinstalling the protocol. The reset command rewrites the
 following two registry keys:

SYSTEM\CurrentControlSet\Services\Tcpip\Parameters\
SYSTEM\CurrentControlSet\Services\DHCP\Parameters\