I was able to remedy the 100% disk usage yesterday.
I uninstalled skype.
I had done some other things Kapil had mentioned, but after uninstalling skype, the usage dropped significantly and the computer was a lot snappier.
If you have multiple users, I would recommend having all user uninstall skype.
It worked for the machine I was having issues with, and hope you will find a remedy for yours as well.