The Sony Portable Reader System, commonly referred to as the Sony Reader, is an electronic book reader that utilizes electronic-paper / e-ink technology to simulate reading on actual paper. Originally released in late 2006 after multiple delays, Sony released a newer model in October 2007 with improved e-ink technology. The Sony Reader runs on Linux and features a 600×800 pixel resolution on a six inch screen supporting eight levels of grayscale. Weighing just 9 ounces with 200MBs of on-board storage capable of holding up to 160 eBooks and an expansion slot capable of supporting up to 2GB SD cards or 8GB Memory Stick Duo cards, the Sony Reader can serve as a portable library holding thousands of books. Besides supporting Sony's proprietary ebook format with thousands of titles currently available for purchase via the Sony Connect Store (accessable via a Windows only application that currently doesn't work on Windows Vista), a variety of free file formats are supported by the Sony Reader, including: Adobe PDF; text and rich-text documents; Microsoft Word .DOC documents; image formats including JPG, GIF, PNG, and BMP; and audio formats including both MP3 and AAC. The Sony Reader is powered by a rechargeable Lithium Ion battery that can support up to 7500 digital page turns per charge. The Sony Reader's major competitor is the Amazon Kindle.