UltraDefrag is a free and open-source defragmentation tool that allows users to optimize their hard drives for faster performance. It supports both 32-bit and 64-bit versions of Windows and can be used on both HDDs and SSDs. The software offers a variety of defragmentation options, including boot time defragmentation and the ability to exclude specific files and folders. Additionally, UltraDefrag includes a GUI interface and a command-line interface for advanced users.