Although Windows 2000 comes with a disk defragmenter, you may still want to purchase a third-party defragmenter to maintain performance on your Windows 2000 systems. The reason is that, according to Microsoft, while the built-in defragmenter takes care of the basics, it is limited in what it can do. A defragmenter maintains disk performance and capacity by rearranging files on the disk to fill in the holes left by deleting files. Without defragmentation, performance of Windows disk systems will degrade over time.
According to Microsoft the Windows 2000 defragmenter is based on Executive Software's Diskeeper defragmenter. However it does not have the full functionality of third party defragmenters and some of the limits may be significant in your installation. In bulletin Q227463 in the Microsoft support knowledge base, Microsoft lists limits on the Windows 2000 defragmenter.
It can only defragment local volumes, only defragment one volume at a time, cannot defragment one volume while scanning another volume, cannot be scripted, cannot be scheduled, and can only run one Microsoft Management Console (MMC) snap-in at a time. Third party manufacturers such as Executive and Symantec say that their defragmenters don't have most or all of these limits.
Whether it is worth spending the money for the additional features of a third party package depends on how you manage disk defragmentation, of course.
Rick Cook has been writing about mass storage since the days when the term meant an 80K floppy disk. The computers he learned on used ferrite cores and magnetic drums. For the last twenty years he has been a freelance writer specializing in storage and other computer issues.