How to "complete" a DVD that was converted from a VHS tape
 

So some time ago my rents converted some VHS tapes to DVD for me to watch on my computer.

I put them in, nothing. Nero sees it as a new DVD. I have used Isobuster, and found there ARE files on there.

I am not sure which VHS-to-DVD burner or whatnot thing my parents used but I am guessing it didn't complete the job so the DVD's made can be played on any DVD player.

Any ideas on how to "complete" the DVD so it will run?

The term is called "finalizing". Your parents should have done this on their DVD recorder.

You should be able to use Isobuster to rip out the files from there, and burn to a new (and finalized) disc.

There MAY be ways to finalize with Nero or IMGBurn if it were DVD+R, but definitely not with DVD-Rs...