You need a reasonable amount of free space, defrag complains if you have
less than 15% but will still run if you force it, but not do a very good
job.
Defrag is actually a cut down version of Executive Softwares Diskeeper.
Find defrag.exe in \windows\system32 and look at its properties, you'' see
under the version tab, the company name is given as
Microsoft Corp. and Executive Software International, Inc.
This cut down version is not bad, considering its free, but it cant
1.Defragment the page file
2. Defragment the MFT (MAster File Table)
3. Defragment folder files
4. Fully contiguise free space.
Diskeeper has lots of nice functionality, you can set it up to run in the
background when there are plenty of free resources and as it thinks is
necessary, an option they call "Set it and Forget it"
It will fully defragment all of the above by being able to run on reboot,
similar to the way chkdsk does.
It has its own scheduler if you want to run it regularly at set times.
Its very very good.
You can get a 30 day trial which has fully functionality. You don't often
get that with trialware these days.
http://www.execsoft.com/downloads/menu.asp
Have a play with it.
Paul