win xp sp2 start>run>cmd>netsh winsock reset

To Reset the Winsock Registry Entries

Click Start >Run >regedit {enter}
Navigate to HKEY_LOCAL_MACHINE\SYSTEM\CurrentControlSet\Services\Winsock and delete it; just below that, see HKEY_LOCAL_MACHINE\SYSTEM\CurrentControlSet\Services\Winsock2 and delete it
Exit Regedit and reboot.

To Reinstall TCP/IP

To do this you need a copy of nettcpip.inf. There is one on the Windows XP CD and there may be one on your hard drive at C:\WINDOWS\inf\nettcpip.inf. Note: To see the inf folder, open My Computer and go to the menu item Tools > Folder Options... > View > and choose Show hidden files and folders.

Right click "My Network Places" select Properties.
Right click the connection(s) and select Properties.
Click Install >Protocol >add >have disk.
Browse to the location of nettcpip.inf .
Select nettcpip.inf then click Open then OK then Internet Protocol (TCP/IP) then OK then Close

above is from here