For the ClockType=24_HOUR parameter to work correctly on Windows NT and Windows 2000, the following fields should be set to 1 in the Registry:
HKEY_USERS\.DEFAULT\Control Panel\International\iDate HKEY_USERS\.DEFAULT\Control Panel\International\iTime HKEY_CURRENT_USER\Control Panel\International\iDate HKEY_CURRENT_USER\Control Panel\International\iTime