IPv6 is not enabled by default in Windows XP.  To enable see below.  no reboot required.
From the command prompt:

ipv6 install
netsh int ipv6 uninstall

IPv6 is installed by default on most new operating systems.  See Below.  This creates a significant security issue which I will post about at a later date.

Vista, Windows 7, Server 2008, [...]

The default interface command erases all commands on the particular interface places the interface in a default state which includes no shutting the interface.  Below is the configuration of an interface before and after running the default interface command.
Sales2#show run interface fastEthernet 1/0
Building configuration…
Current configuration : 128 bytes
!
interface FastEthernet1/0
description Dev Lab
ip address 192.168.3.34 255.255.255.0
shutdown
duplex [...]