Defragment

It will do that as its an application that needs to be run from the command prompt, once the command window is open ( you should in XP find the comand prompt in Accessories folder of the Start > Program > Accessories menu ) but you do know how to get to the C prompt anyways.

once open it will resemble the old DOS prompt window, with a > _ prompt and thats where you follow the commands to defrag the single file,

i.e from the site listed from COMPUABLE, full explanation of the command codes are listed on the link.

where is says file name you will have to enter the full path of the file eg. C:\windows\*.* ( *.* is if you wanted that whole folder defragged only but you could enter a file name )


note: you dont have to use all the command switches highlighted in bold/italic.

 

If you are double clicking contig.exe, then thats not how to opperate this application, you need to open the command prompt window of XP and type the word contig at the prompt, this app is a command line application, its not a GUI app.

easiest way is to copy the contig exe to the system32 folder, then open the command prompt window either by accessories or start > run and typing cmd [enter]

once the window is open you type contig
http://img244.imageshack.us/img244/4302/untitled7ft.jpg

but what I would do as command line apps maybe a bit hard for you to grasp, is to use Womfalc7's suggestion of a that Power Defrag app as its a GUI front end to the Contig app, and thus saves having to use the command line to run it.

 

It will require the same free space on your HD as any other defrag app would , a file can only be defragmented if there is an empty space large enough to hold the entire file, if not enough space it will not defrag.