Larry writes, “How do I change a file extension from VOB to MPEG?”
Presumably you’re looking to rename a VOB file to .MPEG or .MPG so that you can edit the file in a software video editor that doesn’t recognize the .VOB file extension as valid. To change the file extension on a .VOB file to .MPEG or .MPG you simply need to rename the file.
You can’t rename the .VOB file on a DVD because DVDs are read only, so the first thing to do is copy the VOB file from the DVD to your hard drive. Right click the VOB file on your hard drive and choose Rename from the menu.

Delete the .VOB extension and replace it with .mpg or .mpeg.

Assuming you have DVD player software on your computer, the file should now just work almost anywhere you can play .mpg files.
If you can’t see the file extension when you go to rename it, in Windows XP open Windows Explorer, go to Tools > Folder options, click the view tab and uncheck the box next to Hide extensions for known file types before completing the steps above.
For Windows Vista, click Organize > Folder and Search Options , click the View tab and uncheck the box next to Hide extensions for known file types before completing the steps above.