i'd think that the coaster you mean was for rct2 or rct3. Rct1 doesn't really has hacks from as far as i know.
Do what hyyyper said, Check if the file is a td4 file, Also make sure if your ride is in the right folder. Or give a link to the ride you mean. So we can check it out.
EDIT:
http://www.coastercrazy.com/track_exchang ... p?tid=5628
As i can see it's just a rct2 game and accidentally uploaded as rct1...