Microsoft introduced Metafile Image Code Execution (MICE) in Windows NT4. Every version of Windows starting with NT4, including their not-yet-released Windows Vista (aka Longhorn), incorporated this code. As soon as clever hackers discovered it, Microsoft released patches to remove it. Also remember that any fresh installation of Windows will initially be vulnerable to MICE exploitation until it is patched to eliminate this behavior.
Patches are NOT available for Windows NT4, which continues to have MICE and will forever remain vulnerable. This vulnerability can be suppressed through the use of third-party utilities