The other day I pointed out that Apple and Amazon are creating competing video download services.

Amazon's Unbox offering video downloads went live yesterday. The new service is Amazon.com's flashy foray into the hot digital download market, where the e-commerce behemoth is trying to stake its claim as the online retail business begins to mature.

To start watching the content, customers must download the Unbox player and can transfer the films and shows to Windows Media video-compatible portable devices.

Unlike iTunes, Amazon Unbox doesn't sell music tracks. It may make sense for Amazon to add them to the service in the future. Analysts say that Amazon, of Seattle, could be holding off on entering the digital music market until its video service gains traction. With 37.6 million unique visitors to its site in July, Amazon is the ninth most popular Internet brand, according to Nielsen/NetRatings.