To be helpful, I would need more information. What is the make/model of your motherboard, HDD, GPU, CPU, RAM, PSU? What operating system are you running? What programs are you running when the freezing occurs?
Well using a WDC green for an OS drive WAS a bad idea as they are designed to be both quiet and SLOW. they also go to sleep after a very short idle time(this can result in about 4-5 seconds of spin up time after it goes to sleep.).
My last hdd broke so i was forced to use this for my OS, but it works fine. For the temps im a cool freak so everything runs at 30-40 Idle 50-60 under load. I have security essentials not running, so ill uninstall avast then.
If you think that it MAY be a parking issue with the drive, see if CrystalDiskInfo has an option under Function -> Advanced Features -> AAM/APM Control. If it lets you Disable APM, it will keep the drive from parking until the next reboot. Please note that doing this can make ANY drive with a g-sense motion sensor report vibrations very easy(more of a test solution).
Im downloading crystal disk info and the psu will never be a problem, I got an 800w from a friend. Ive also got a thing that comes whith the mobo that monitors voltage and temps of everything as well as RPM of the fans.
Please keep an eye on the SMART status with CrystalDiskInfo if you can(check it once a day or something). Look at the reallocated sector count. You want this to be ZERO.
I am saying this because I saw a drive that was doing something similar and the owner thought it had been fixed by a defrag. That just triggered the drive to remap some sectors. As more bad sectors build up the drive fail very fast and data recovery was hard.
I do not want you to have to put up with a drive failing very fast.