How can I reinstall a game on my computer that is unable to be uninstalled?

A while ago I purchased Civilization IV, and successfully installed it. I it for a while, and eventually wanted to uninstall it to free space on my computer (Vista). when I went into Programs and Features and clicked uninstall Civ. 4, I was given an error message saying, "An error (-5001 :0xffffec75) has occurred while running the setup." I then restarted and came up with the same error. I got frustrated, and went into the install folder and deleted everything (probably not my best move). Now, everytime I run the game on the disk, I get the play on, but nothing happens. there is no uninstall on in the autorun menu. I can not uninstall the game, or run the game. I would really like to be able to play it again. Can someone tell me what I should do in order to play this game again?