If you want to clear everything on the harddrive, then you are referring to reformatting.
System restore or system recovery are both terms that mean things such as system recovery to a certain checkpoint, and that doesn't wipe the whole harddrive clean.
All Window's PC, I'm not sure about Mac, Linux, and other OS's, have a CD disk they give you once you set up your computer the first time around. You will have to use that to do it the proper way of reformatting.
You can also download a .iso from sites like TPB and install that copy of whatever Windows version and that will also wipe the entire harddrive clean as well.
If you have anymore questions feel free to PM me about it.
Have a good day~