As much as I loved the old beloved Transport Tycoon Deluxe, it's days are done IMO. OpenTTD, the open-source clone, reached version 1.0.0 earlier this year (current version as of this post is 1.0.1). The game now comes complete with its own original sets of graphics, sound and music. You no longer need to download any part of TTD in order to play OTTD. It runs on Windows, Linux, and to some degree, MacOS X (currently not maintained due to lack of developers who can fix bugs, but it can be compiled and runs OK for the most part).
Check out OpenTTD at
http://openttd.org/ as well as its excellent online community at
http://tt-forums.net/ where you can find enhancements such as alternate music sets, expanded trains/vehicles/aircraft sets, new buildings, roads, industries and more.