I'm no expert...probably the .dll file is corrupted, or something. Usually you can download those and fix the problem. I would try and find some technical support on WinDVD's website first--they may even have a patch or something to fix the problem. Beyond that, I normally Google the exact words of the error message. There's an excellent chance someone else has had the same problem as you, and they've gotten help from more technically-minded people than me on a tech forum. Good luck!