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What is it?
Windows Defrag - dfrgntfs.exe
What does it do?
This is the process in Windows
2000 and XP that handles the file defragmentation process. This helps
to speed up things like opening and reading files which will make it so
that your applications run as fast as they can on your system. NEVER
end this process, if you do it can cause corruption in whatever file it
was processing when you ended it.