It is legal to back up anything you own for your own personal use. The MPAA doesn't like that and tries to tell you otherwise, but it's how software like DVDx, DVD Decrypter, DeCSS, etc. is legal. DVDXCopy was shot down only because the courts ruled that it was used primarily for illegal uses, not legal ones as it claimed.
If you download a version of something you don't own then it's illegal. e.g. if you own a VHS copy of Ronin and you download a DVD-rip of it, it's illegal; but if you own the DVD that the rip was made from it's technically legal. (more accurately, not illegal, as there is no specific law stating such action is illegal or legal)
When you buy a movie or a CD you have full rights to do with it whatever you want, provided it is not for profit and doesn't violate certain fair use laws. (like public exhibition) Converting a VHS tape to DVD is completely legal; it's no different than converting it to any other media format. While the package it comes in might be different, the content is what's key. Unless you add in content from sources you didn't pay for, it's completely legal.