Did you backup your User folder? This would have all of your data including custom content in it. If you did, you can easily restore the data by doing a fresh install of TRS2006, updating to SP1 if needed, then importing your content.
If you do not have a back-up, like jcitron mentioned, you will need to buy a FCT in order to download content from the DLS or get a newer version of the game if you like to do so without buying a FCT.