This might sound like a stupid question but as far as I know, when you buy games on Steam they are yours forever as long as you remember your account info and you can download those as many times as you want on as many machines you want as king as you use your Steam account to play them... Does this rule work if I activate Skyrim on Steam ? I mean as long as I have a copy of Skyrim and a Steam activation key I can use it as many times as I want, right ?

The thing with "Steamworks" games regardless of if you buy a physical disc or buy a digital copy, they act just like any other steam game. So to answer your question, yes, Skyrim will work just like any other steam game, and can be played on any number of computers for the life of Steam.

Thanks Good to know before buying it

Also, forgot to ask if I buy the activation key, do I have to buy Skyrim CD or vidrtual copy ? Or is activation key enough ?