The Windows Disk Defragmenter, discussed in the article Defragmenting your hard disk in XP does not defragment the system files which are being used by Windows. For example, the virtual memory file or the page file. Mark Russinovich of System Internals has made a free utility for defragmenting these files. You can download this tool from the Microsoft Technet page at http://technet.microsoft.com/en-us/sysinternals/bb897426.aspx
Run the PageDefrag tool and look at the number of fragments of all the listed files. If the number of fragments of each file listed is 1 then you do not have to defragment. If the number of fragments are more than 1, then you can defragment. Run PageDefrag and select Defragment at next boot and click OK as shown in the picture below :
After clicking OK, restart your computer and PageDefrag will start to defragment the system files as shown in the picture below. Once it has finished, system will boot into Windows.
If you want, you can choose to defragment the PageFile at every boot. Just select Defragment every boot in the main PageDefrag window as shown in the above picture.
Note :
PageDefrag runs only on the 32-bit version of Windows XP.