The tcp-ip protocol cannot be reinstalled on Windows Xp. You can only reset it using a command line utility.
1. Type "cmd" at a run command to open up a command prompt window.

2. type "netsh int ip reset C:\resetlog.txt" at the command prompt. the last part of the command is just a path for the log file the command creates. You must type the log file path or "netsh" will not complete the command. This command will edit the registry and place tcp-ip back to it's original pristine state of when the OS was first installed.

3. Reboot you computer.
Microsoft Knowledge Base Article - 299357 |