Open source disk tool UltraDefrag hits version 4.0
Ultra Defrag is packed with functionality, offering whole disk defragmentation and optimization, file and folder defragging (via your right-click context menu), boot-time defragging, and scheduled jobs. The boot-time job allows UltraDefrag to take care of locked system files like pagefile.sys and your registry hives, which are locked while Windows is running.
While UltraDefrag v4.0 isn't the project's first major release, its developers consider this to be the first 'non-beta' due to past issues with reliability. The new version is fast, and after testing it on three different Windows 7 systems (including x64) those problems seem to have been fixed.
Downloads are available for both 32 and 64-bit Windows versions, and both an installer and portable option are provided.