Personally, i still prefer use IPv4. In Windows Vista and Windows 2008, IPv6 is enabled by default. I've created a small script to disable IPv6. Here is a content of my DisableIPv6.bat:

@Echo off
@ECHO Windows Registry Editor Version 5.00 > %TEMP%\DisableIPv6.reg
@ECHO [HKEY_LOCAL_MACHINE\SYSTEM\CurrentControlSet\Services\Tcpip6\Parameters] >> %TEMP%\DisableIPv6.reg
@ECHO "DisabledComponents"=dword:000000ff >> %TEMP%\DisableIPv6.reg
REGEDIT /S %TEMP%\DisableIPv6.reg