PageDefrag is a program, developed by Sysinternals (now distributed by Microsoft), for Microsoft Windows that runs at start-up to defrag key files such as the virtual memory page file and the registry files.

If these files are defragmented, this may improve performance. Since PageDefrag only affects a small number of files, it takes a comparatively short time to run when compared to entire-disk defragmenters like Windows Defrag.

PageDefrag does not defragment the contents of the registry files, only the placement of these files on the hard drive. Numerous other utilities like NTREGOPT examine the contents of the registry to optimise it.

PageDefrag runs on Windows NT 4.0, Windows 2000, Windows XP, and Windows Server 2003.