PCS:Black screen CTD before Oblivion fully launches
Oblivion crashes to the desktop quickly, before the game has even completely launched.
Causes and Solutions
Cause 1 - UAC Protection
Windows 7 and Windows Vista users have User Account Control (UAC) on by default, which prevents applications without administrator privileges from installing and modifying files. Oblivion has to modify a few files, such as its main configuration file, in order to work fully.
Solution #1: This issue affects many utilities for Oblivion, so the cleanest, safest method to avoid this and further related issues is to uninstall Oblivion and install Oblivion to a folder outside of UAC protection (i.e., C:\Games). The same applies to Steam, if Oblivion is installed through it.
Solution #2: It is possible to only disabled UAC protection on the folder in which Oblivion is installed. Since Oblivion and other mods modify Documents/My Games, you may need to disable protection on that folder as well.
Solution #3: Another clean method (albeit a bit less safe) is to turn off User Account Control all together.
User Account Control