I just installed Oblivion and I have two questions. First of all, I have the GOTY, but installed the Oblivion instead of SI patch. I know I have to uninstall and reinstall Oblivion to add the correct patch, but do I also need to uninstall the second disc (SI and KotN) files? And if so, do I just manually deletevthem since there is no uninstaller and they are not removed when I uninstall Oblivion?

And my second question: when I play Oblivion, the game screen seems to be slightly off center, with a very thin white line on the top and right side. Any ideas how to fix this?

The GOTY edition is already fully patched, there's no need to do anything to it. Just install and play. You need to install all the files though as the patch will be the last to be added.

Using any in-game Anti-Aliasing?

Okay, so I don't need any patches, I'm going to reinstall to make sure installing the patch on my own didn't mess anything up then. Any advice on what to do about disc 2 content when I reinstall (since it doesn't have an uninstall option) . . . Leave it be, delete and reinstall, or just reinstall (would that create a duplicate?).

And I had anti-aliasing on 2X, could that be the problem?

Shivering Isles installation modifies the already existing bsa files, and updates the oblivion.exe. The SI esp file doesn't really do anything, aside from enable the additional content. So, uninstalling oblivion, and nuking the installing directory, and the one in my games should pretty much take care of it for you. Once installed, you simply can't uninstall JUST SI......

You can uninstall the DLCs through the Control Panel option that removes programs, you'll find them all in there. Or you can simply delete all the files in your Data folder, it won't affect your game at all. Only Shivering Isle makes changes to the game itself, all the DLCs work the same way as any mod you download.