DVD burners have emerged as a hot Christmas item this year -- but consumers need to consider the "pluses and minuses" of what they're buying. The machines allow people to create their own DVDs, just as CD burners let users make compact discs of their own design. But they come in two main varieties. What many consumers don't know: The burners they're buying may not work with the DVD player they already own. As with any new technology that has rival formats -- remember VHS vs. Beta -- there's a fight under way between manufacturers over which standard will dominate the market. It's too early to say which version -- the "plus" version or the rival "dash" format -- is going to succeed. The issue is important because some DVD players read discs made in one format, but not others. The clash is moving to center stage because consumers are beginning to flock to DVD burners the way they did to compact-disc burners. World-wide shipments of DVD burners are expected to more than double this year, to 5.07 million, compared with just 1.42 million last year, according to technology research firm International Data Corp. The firm projects the number will shoot up to more than 14 million next year. ALLOWED You can make copies of your own home videos or copy collections of home-shot movies from videocassette onto DVD, since that material belongs to you. Most legal experts also say that consumers can burn DVDs of free broadcast television shows (an episode of "Friends," for example) for their own "time shifted" home viewing. NOT ALLOWED Making copies of a DVD or videocassette feature film that you bought crosses the legal line, according to movie studios. (Some people argue that there may be "fair use" exceptions, like teachers using material for a class.) Also generally not allowed: downloading a copy of a Hollywood movie from one of the free (but unauthorized) Internet services like Livewire.com.