defrag.exe is a process associated with Windows Disk Defragmenter from Microsoft Corp. and Executive Software International, Inc..
It is included with Microsoft Windows OS.
Non-system processes like defrag.exe originate from software you installed on your system. Since most applications store data in your system's registry, it is likely that over time your registry suffers fragmentation and accumulates invalid entries which can affect your PC's performance. It is recommended that you check your registry to identify slowdown issues