If you have a desktop shortcut for Oblivion, you can probably figure out where the game folder is by right-clicking the shortcut and looking at Properties. One of the tabs should show the program location. If you don't have a desktop shortcut, you can probably find a shortcut in your Windows Start Menu (you can right-click and choose Properties for that too).
The location of the game folder will vary depending on where you bought the game (Steam, GOG, or disc) and version of Windows, as well as whether you installed into the default location.
The game's save folder is usually somewhere else (unless you're using Windows 95/98/ME). On Windows 7 the save folder is often in one of the subfolders of
The AppData folder is hidden unless you enable display of hidden files.
If you have a Steam version, here's a video showing where they buried Oblivion's Data folderhttps://www.youtube.com/watch?v=KHzFhKqk6aw