Thought so. If you haven't downloaded the vp files from the FTP (or anywhere else for that matter) and then deleted the contents of your data folder they will take precidence.
About the only thing you can do is copy the entire data folder and then use VPView to extract the contents of the DEM VP to Data. Once you're finished with it you can just delete it and replace it with the copy you made (having first copied your pilot file back over).
To be honest you'd be better off getting hold of the VP files from the FTP.
EDIT : Actually you could just back up the texture file that is on the TC-TRI and replace that. Much simpler. You'll need to do the above if you want to play something like Inferno though.
EDIT 2 : Or you could use FS2_Open make a folder called DEM. Put a folder called Data inside that and then extract the contents of the VP there. When you run with the -mod DEM switch the mod would run as higher priority than the contents of Data.
Still think you're better off getting the VP files though
