That's the problem with forums, we can't see the people behind the posts.
Blackwatch didn't mean anything by his post as he like everyone else was not in possession of all the facts, I don't think his post is out of line based on the posts previous to this and the information we had to go on.
We now know the situation so are in a better position to help you appropriately.
I'll try a step by step guide, this usually helps, as you mention it may or may not solve your problem but this is as far as we can reasonably give help to others on the forum. If this doesn't work, short of someone coming round and doing this for you there's no other solution!
Bear in mind here I don't have TC3 so I'm using TS12 CMP and hoping it's the same!
If anyone out there has TC3 and notices any differences feel free to correct my guide shown below:
1. Double click yout TC3 icon
2. Click the content option, this opens content manager
3. In the search box on the left first click clear then type class 50 horn
4. The one you have installed on your pc will show a little black laptop computer symbol next to it. It is kuid2:68236:1030:2, this reference is displayed on the right of the content manager screen
5. Right click on this asset select edit, then another screen appears and select edit in explorer
6. The asset then opens up and displays a windows explorer screen, anyone using a pc will then be familiar with this format
7. Locate the config file, it will be easily noticable
8. Double click this file and it will open in notepad
9. Look for the line:
Trainz-build "2.9"
10. Change the "2.9" to "2.8"
11. Save the file (Click file then save option)
12. Close the asset with the x at the top right corner
13. Go back to the content manager screen, right click the asset then select edit, another screen then pops up and select commit
14. If the asset shows a red exclaimation mark there has been an error in this process, let us know if this happens and we will take it from there
I really hope this helps you, it does seem complicated but it isn't really, it is just that I've been extremely concise with my guide in order to help you out.
Let us know how you get on with this if you decide to take up the challenge!