Both Piriform Defraggler and Windows defragmentor are freezing my computer when running individually on my computer. How can I fix this?
You should start by posting system information. Which OS? Which Version of defraggler? What is your hardware? My guess is that the HDD is getting old and thus CPU usage is high (a lot of idling) because it's waiting for data. I had this on an old IDE drive. One core would consistently use 100% because it was constantly waiting for the slow dead drive to deliver.