Open up the folder mentioned in the error message.
Delete the contents (not the folder!) The process may take a few minutes and may appear to hang but it's not hung. Once done, try again.
If that doesn't work then this isn't a good thing to see. Your hard disk may be failing and the data is residing within a bad block. If you can, backup Trainz content folder to another hard disk such as an external backup drive and then run the chkdsk utility.
You can do that by opening Windows File Manager.
Open up This PC
Right Click on your drive that has your data on it.
Choose Properties
Then click on the Tools tab.
Click on Check drive for errors.