If you uninstalled TCP/IP and can't reinstall install it, use regedt32 to delete the following keys (and their sub-keys):

<b>
HKEY_LOCAL_MACHINE\Software\Microsoft\DhcpMibAgent
HKEY_LOCAL_MACHINE\Software\Microsoft\DhcpServer
HKEY_LOCAL_MACHINE\Software\Microsoft\FTPSVC
HKEY_LOCAL_MACHINE\Software\Microsoft\LPDSVC
HKEY_LOCAL_MACHINE\Software\Microsoft\NetBT
HKEY_LOCAL_MACHINE\Software\Microsoft\RFC1156Agent
HKEY_LOCAL_MACHINE\Software\Microsoft\SNMP
HKEY_LOCAL_MACHINE\Software\Microsoft\SimpTcp
HKEY_LOCAL_MACHINE\Software\Microsoft\Tcpip
HKEY_LOCAL_MACHINE\Software\Microsoft\TcpipCU
HKEY_LOCAL_MACHINE\Software\Microsoft\TcpPrint
HKEY_LOCAL_MACHINE\Software\Microsoft\Wins
HKEY_LOCAL_MACHINE\Software\Microsoft\WinsMibAgent
HKEY_LOCAL_MACHINE\SYSTEM\CurrentControlSet\Services\DHCP
HKEY_LOCAL_MACHINE\SYSTEM\CurrentControlSet\Services\DhcpServer
HKEY_LOCAL_MACHINE\SYSTEM\CurrentControlSet\Services\FTPSVC
HKEY_LOCAL_MACHINE\SYSTEM\CurrentControlSet\Services\Lmhosts
HKEY_LOCAL_MACHINE\SYSTEM\CurrentControlSet\Services\LPDSVC
HKEY_LOCAL_MACHINE\SYSTEM\CurrentControlSet\Services\NetBT
HKEY_LOCAL_MACHINE\SYSTEM\CurrentControlSet\Services\SimpTcp
HKEY_LOCAL_MACHINE\SYSTEM\CurrentControlSet\Services\SNMP
HKEY_LOCAL_MACHINE\SYSTEM\CurrentControlSet\Services\Tcpip
HKEY_LOCAL_MACHINE\SYSTEM\CurrentControlSet\Services\Wins
HKEY_LOCAL_MACHINE\SYSTEM\CurrentControlSet\Services\WinSock
HKEY_LOCAL_MACHINE\SYSTEM\CurrentControlSet\Services\WinSock2
HKEY_LOCAL_MACHINE\SYSTEM\CurrentControlSet\Services\<NetDriver>x\Parameters\Tcpip</b>
where <NetDriver> is the name your NIC and x is the number.

You may have to use Regedt32 / Security / Permissions to grant Administrator Full Control, before you remove the following keys:

<b>
HKEY_LOCAL_MACHINE\System\CurrentControlSet\Enum\Root\Legacy_DHCP
HKEY_LOCAL_MACHINE\System\CurrentControlSet\Enum\Root\Legacy_Lmhosts
HKEY_LOCAL_MACHINE\System\CurrentControlSet\Enum\Root\Legacy_LPDSVC
HKEY_LOCAL_MACHINE\System\CurrentControlSet\Enum\Root\Legacy_NetBT
HKEY_LOCAL_MACHINE\System\CurrentControlSet\Enum\Root\Legacy_TCPIP
HKEY_LOCAL_MACHINE\System\CurrentControlSet\Services\LanManServer\Linkage\Bind
HKEY_LOCAL_MACHINE\System\CurrentControlSet\Services\LanManWorkstation\Linkage\Bind</b>
Shutdown and restart your computer.

You should now be able to install TCP/IP.

NOTE: Don't forget to re-apply your latest Service Pack, after the TCP/IP install.