System Protection is turned off. To turn it back on so you can use System Restore, see Turn System Restore on or off.
I went to turn System Protection on, and this is what the screen looks like:
How exactly should I turn it on, to be safe? (I was recently infected by malwares.)
Also, I never upgraded to Win 7 or anything or using anything like dual-boot. It's a Dell desktop, if that matters.