HWMonitor doesn't work on my system. It just displays an almost blank window with the name of the computer. Help has nothing. Clicking on privacy policy links to a non-existent page.
I would go with RealTemp or CoreTemp than. The one advantage to RealTemp is you can calibrate your sensors to get a more accurate reading. I would just stay away from SpeedFan, as in my experience it isn't as accurate.
There is nothing to be worried about when installing CoreTemp. It isn't changing anything, just install the program, which technically is a change to your system
Core temp should work fine. It will ask you if it can make changes becuase it access hardware. I use Windows 7 64bit with a C2Q. does it for me.
I've not tried Real Temp on this machine so I can't say.