Some of the files within the TW games (eg .db and .world files) are in a binary format that is best viewed with a Hex Editor.
There are a variety of free or cheap hex editors available. Various members of the community have recommended: http://www.chmaas.handshake.de/delphi/freeware/xvi32/xvi32.htm which has a good data inspector feature and an encoding function.
Others such as http://mh-nexus.de/en/ have copy and paste functionality and a file comparison capability.
Non-free hex editors such as WinHex are also used by some modders, many more are available.