So I installed Oblivion and it worked fine. Then I installed the DLC and knight of the nine and Shivering isles. Then I installed the official patches and the unoficcial patches. And now the game doesn' start. I click play on tha launcher and it happens nothing, only a little black box on the left up corner of the screen... Any ideas on how to solve this?

Thanks

Remove the unofficial patches, and then see if Oblivion starts up. If so, enable them one by one until you find the issue.

I found the issue, for some reason oblivion was trying to run the battlehorn DLC and i didn't install that... deselecting the battlehorn dlc and it now works