Morrowind and Oblivion errors

Ok, this is my first post on TES wiki, even though I've played all games in the series. Recently I tried to replay Morrowind and Oblivion, but I traded both games some time ago. I wanted to buy the Anthology, but it's sold out in my country. So I decided to download goty editions on the Iso Zone site (I'm not proud of this decision). I installed both games and all expansions and when I tried to play them it said that disc is required to play. Can anyone help?