After much bluster and a few false starts, high-definition DVD has arrived. You'll find several products meant for the living room and for the PC at your favorite store, with more on the way. Unfortunately, high-def DVD comes in two, incompatible formats--Blu-ray Disc and HD DVD--and the formats' supporters have not resolved their differences. That means buyers must carefully weigh their options while everyone waits to see which technology will reign as successor to DVD, both as an entertainment medium and as a storage medium. You may want to wait before you lay out your cash.

Both Blu-ray Disc and HD DVD measure 12cm in diameter, the same as a standard DVD. The formats physically differ in where the data lies on the disc: On Blu-ray, data is closer to the surface of the disc than it is on HD DVD.

Find out more about the HD DVD vs Blu Ray battle at http://www.washingtonpost.com.