The PageDfrg help file contains:

PageDefrag                               Copyright © 1998-2000 Mark Russinovich                               SysInternals                               Introduction                               One of the limitations of the Windows NT defragmentation interface is that it is not possible to defragment                               files that are open for exclusive access. Thus, standard defragmentation programs can neither show you                               how fragmented your paging files or Registry hives are, nor defragment them. Paging and Registry file                               fragmentation can be one of the leading causes of performance degradation related to file fragmentation                               in a system.                               PageDefrag uses advanced techniques to provide you what commercial defragmenters cannot: the ability                               for you to see how fragmented your paging files and Registry hives are, and to defragment them.                               Using PageDefrag                               When you run PageDefrag (pagedfrg.exe) you will be presented a listbox that tells you how many clusters                               make up your paging files and Registry hives (SAM, SYSTEM, SECURITY, SOFTWARE, .DEFAULT), as                               well as how many fragments those files are in. If you feel that these files are fragmented enough to                               warrant a shot at defragmenting them, or if you want to defragment them at every boot, select the                               appropriate radio button choice and click OK.                               When you direct PageDefrag to defragment, the next time the system boots it will attempt to do so.                               Immediately after CHKDSK examines your hard drives PageDefrag uses the standard file                               defragmentation APIs (see for documentation of these APIs) to                               defragment the files. As it processes each file PageDefrag will print on the boot-time Blue Screen the file                               name and its success at defragmenting it. If it is successful at reducing the fragmentation it will tell you                               the number of clusters the file started with and the number it consists of after the defragmentation.                               In some cases PageDefrag may be unable to reduce fragmentation on one or more of the files, and it will                               indicate so on the boot-time Blue Screen. This can happen either because there is not enough space on                               the drive for defragmentation, or the free space itself is highly fragmented. For the best results you should                               use PageDefrag in conjunction with a commercial defragmentation utility or the free Contig defragmenter                              at