Adjusting files without asking

I recently installed LoL for the first time and I am viciously confused as to how it allows itself to change files without asking. I did NOT agree to ANY terms or conditions, which confused me as usually you MUST agree before continuing. I had a disruption before my second match, freezing my screen, crashing my PC and then re-opening itself once my PC restarted. I uninstalled LoL as soon as I could. Unfortunately, as I uninstalled the game, 6 of my taskbar icons disappear, and my PC crashes AGAIN. I have never had issues with any other game in this way. Please give a warning of some sort if you intend to change or damage our computers, thank you.