If you really want to make a DVD into a VCD, then Roxio's Toast is your friend. Set it to make a VCD and drop any QuickTime-compatible movie (you can use other formats too, if you can download the proper software to make QuickTime play it) into the window, and it will do the rest
As others have noted, you probably want an SVCD rather than a VCD, but a cheap DVD burner really is the best option.