HELP needed-accidently deleted oblivion files now can't reinstall

[samanand]

Hi, I accidently deleted Oblivion but whenever I try to reinstall I get asked if I want to uninstall oblivion. I've since deleted all relevant entries(as far as I know)in the harddisk and registry. But still instead of installation window I get uninstallation window over and over again.
I've finished the game but want play the expansion now. Please help.

[renegade600]

go ahead and uninstall then reinstall.

[samanand]

Tried that but after uninstall I only get play option not installation option and when I hit play it tells me so and so files are missing and therefore I must reinstall. Only I wish to hell I knew how. And thanks