COD4 Console Reset

[Green Gigs]

Do any of you COD4 players know if there is a command in COD4 that will reset everything in the console back to default? I have looked over command lists from google searches and see "cvar_restart". What is the differance between a cvar and dvar? I know cvar stands for command variable. I commonly see warnings in manuals about damage caused by bad settings in the console. Exactly what type of damage are they talking about, damage just to the game or even the operating system?