Abstract: The present invention relates to an apparatus and method for defragmenting a disk drive in a computer system. The defragmentation process, in accordance with the present invention, determines which files have a high degree of fragmentation, where such file extents are to be physically moved on the disk and further determines which portions of such files are to be moved to the selected physical location. More particularly, the defragmentation process selects each file on the disk, checks to see if the file is excluded from processing and, if not, recovers the extent list for the file. If the file is fragmented, the process determines if there is sufficient free space in which to move the file extents to contiguous location on the disk. If such as space exists, the file extents are moved. If the free space is sufficiently fragmented or the disk is substantially full, contiguous files are moved to contiguous locations so as to partially defragment the file.