With the market for external hard drives for PCs and laptops growing increasingly saturated, Western Digital is now tapping the TiVo market. It announced Tuesday that its $200 My DVR Expander will allow TiVo subscribers to store up to 300 additional hours of standard-definition movies and TV shows. With TiVo's high-definition model, it can store 60 hours of HDTV. Indeed, the device could turn out to represent an alternative to disc devices such as HD DVD and Blu-ray, especially if high-definition movies could be delivered to subscribers automatically via TiVo digital video recorders.