drtweak :
Things I would try.
1) Install Crystal Disk info. See if it says anything other than Good on the drive. If it says Caution or Bad post back what it says
2) Try it in another PC and let it sit. See if you get the same noise
3) If you have another hard drive that is as big as all the data (not your HDD Size itself) you can make a clone using macrium reflect. I have a tutorial here
https://www.youtube.com/watch?v=vlZm5w99pGM&t=
Then do a clean install of windows and let it sit.
So my next step/conclustions would be
1) if bad or caution then drive is failing. if good move to 2
2) If it stops making a clicking noise then it may be something that is accessing the hard drive. I would start the PC up in safe mode (Windows 7 and older mash the F8 key and select JUST safe mode For 8 and newer Hold shift key when click on restart and hold it until the menu pops up (don't have to but hold it the whole time just in case) Then select advanced and then change startup. Then on next restart select the number for just Safe mode. let it sit. if it stops then you have software accessing the hard drive probably.
3) If you go this router and it still happens after a clean install it may be the hard drive going out possibly even though Crystal Disk Info says good.
There are all kinds of ways a hard drive can fail. Crystal Disk Info tells you the health of the disk surface and some read errors which could point to bad/failing heads.
Now you sure it is powering off and on or is it clicking?
I've checked S.M.A.R.T info and it's all good. I double checked in CrystalDiskInfo as well.
It's not clicking, I hear it spinning down and spinning back up a couple times per minute and I just am worried it will cause excess wear on the drive. It only does it when I am not using the computer, if I'm using it it works fine and stays running. I'm not thinking it's a drive issue, I think it's some software issue with windows or my laptop that's causing it to do this. I'd try it in another computer to see if the same thing happens but I don't want to boot windows on another system because then it would install more drivers and stuff.