Otherwise if you want to stay on Windows 7 here is an option for you to try. Your initial OS boot time will increase and it can take a few seconds longer for a program to load up for the first time since a reboot but you will see a drop in disk usage.
Open the RUN box by holding down the windows key and pressing the letter R.
Type in
services.msc
and press enter.
Then scroll down to Superfetch and stop/disable to service
then scroll further down to Windows Search and stop/disable.
You should see and immediate drop in disk usage at this point. If you'd like you can restart you PC and then see it. Also, if defender/security essentials is currently running a process just take a chill pill and wait for it to finish.